Mila has done very well for herself, but there’s no way you don’t put Ashton Kutcher at the top of that cast as far as post-show success.
I happened to see a “Where are they now?” piece about the popular but IMHO not very good '90s sitcom Family Matters on Huffington Post the other day. I’d heard before what became of the actress, Jaimee Foxworth, who played the younger daughter on the show. In terms of her acting career she’s not only the least successful former cast member of this particular show but probably one of the least successful former cast members of any popular show. She apparently never did mainstream acting work again, and starting doing porn once she reached adulthood. She eventually wound up on Celebrity Rehab with Dr. Drew.
Of the other members of the main cast of Family Matters, none are superstars but several have been getting steady work doing guest/supporting roles on various shows, voice work, etc. I don’t know who’s made the most money, but it looks like the young actor who played the little nephew Richie on the show, Bryton James, may be the most successful in terms of having the longest running role in a series. He’s been on The Young and the Restless for nearly a decade.
If we count minor characters on Family Matters then the biggest star currently must be Naya Rivera, who had a small role as Richie’s friend. She now plays Santana on Glee, a part that was basically “Cheerleader #2” in early episodes of the show but soon became a major role. My prediction would be that she’ll wind up one of the more successful post-Glee performers, although time will tell.
Why does that never happen to the ones I want it to happen to? No, they go off and marry rock stars or have passably good careers. :mad:
Parker Lewis Can’t Lose:
Most - Abraham Benrubi (Larry Kubiac) was more popular than Cory Nemec (Parker Lewis) after the show with his roles in ER, Men in Trees and voices on Robot Chicken.
Least - It’s almost a tossup. All of the other cast members aside from Benrubi, Nemec and Tim Stack went on to do nothing. John Pinette (the coach) didn’t do much more TV, but he has a successful (waxing and waning) stand-up career. The principal did voice work (Rugrats), the “cool best friend” went in to sound production.
The sister, the nerdy best friend and the arch nemesis all basically quit acting. I guess the sister, Maia Brewton, wins by default - she has only 1 post-Parker credit while the other two have 3.
Voice work, a glorified cameo, and more voice work. Don’t get me wrong, I love Alan Tudyk, but he doesn’t compare to Fillion.
By the way, Fillion’s tally also includes a starring role in Slither (which was so, so great), voicework in a ton of DCAU movies, the co-lead in Waitress (which was critically acclaimed), Dr. Horrible, and another short-lived show, Drive (which also starred a pre-fame Emma Stone).
I guess it depends on whether or not you think his turn on Two and a Half Men counts as successful. Because to me, he’s got a handful of forgettable rom coms, Punk’d, some commercials, and a job as a sleaze bag in real life. Mila, on the other hand, appears upwardly mobile, has a better range in more dramatic and edgier fare and doesn’t need to go back to TV to have any sort of career. So I guess that makes it my apples to your oranges. Wanna make a fruit salad? 
Malcolm in the Middle
most - Bryan Cranston (Hal)
least - maybe Christopher Masterson (Francis)
I tend to think the Mila Kunis / Ashton Kutcher one is a tossup. He’s been in more than a few rom-coms; he’ll be Steve Jobs in the upcoming “Jobs” movie, he was the lead along with Kevin Costner in “The Guardian” and has been the lead or co-lead in several other movies before and after “That 70’s Show”.
She’s definitely on the upswing, but I don’t know if you can call her more successful.
Highest paid actor on television, isn’t he?
That role isn’t likely to get him any more roles. He chewed the scenery so bad you could see the teeth marks. Granted his character was supposed to be crazy but he was just too crazy. More mainstream actors seem to think soap acting has to be over the top so if they end up in soaps they just don’t do well, but at least he made the resident ham actor look good.
I guess she was successful in hawking exercise equipment and had some small roles in TV series and film. Ritter was an accomplished actor, appearing in Sling Blade, Bad Santa and others, and had a much heavier acting career following the series.
Family Ties:
Most: Michael J. Fox
Least: Tina Yothers
How bout Norther Exposure?
For the least successful… probably Elaine Miles. Hasn’t done much since the show ended in 1995. Peg Phillips was in 7th Heaven IIRC, and most of the other actors / actresses were in a movie or two, even Darren E. Burrows was in a few big films like Amistad. Although, to be fair most of the cast has dropped off the face of the earth except for Rob Morrow and John Corbett. Janine Turner has had some credits, but nothing really noteworthy.
Most successful? Rob Morrow was in Numb3ers, and did several small parts in movies and a couple big parts - like Quiz Show and that one where he played John Wilkes Booth. John Corbett was in My Big Fat Greek Wedding and Raising Helen. Plus, he’s been shacking up with Bo Derek for years, which sounds pretty successful to me.
Of course, of all the people who appeared on the show, Jack Black takes the cake. He did a bit part in one episode halfway through the series-- playing a high school senior --, and from what I remember he was on screen for maybe three or four minutes total. He had a few credits by that time, but all small parts and I doubt anyone at the time knew who he was, and didn’t for sometime thereafter.
And don’t forget he was a preacher in The Waltons. But that was before Three’s Company so it probably doesn’t count. 
I’m surprised no one has mentioned the famously successful alumni of Freaks and Geeks. Most successful would be a toss up between James Franco, who is more critically respected, and Seth Rogen, who is probably the richest, with Jason Segel getting an honorable mention.
(Though if we’re allowed to include non-performers, Judd Apatow would be the real winner here.)
Least successful: Of the main cast, it would have to be either Samm Levine or Martin Starr, though both are busy, in-demand actors. Of the supporting players, it doesn’t look like Natasha Melnick (who played Cindy Sanders) has had much film or TV work recently.
She starred in her own TV series.
:smack:
I would say Julia Louis-Dreyfus is the unequivocal winner here. Jerry Seinfeld will probably always be a “bigger” star just on the strength of Seinfeld, but she has done much more significant work since. The New Adventures of Old Christine was one of the more successful sitcoms of the '00s and netted her five Emmy nominations, and Veep has already won her one Emmy. (She’s won Emmys in three consecutive decades for three different shows.)
Seinfeld’s absence from the spotlight has been voluntary, and I’m sure he’ll always have the ability to get anything he wants greenlit, but the only two high profile projects has has been involved with, Bee Movie and The Marriage Ref, have both been disappointments.
She was also a headliner in Step-by-Step from the old TGIF line up which ran… beats me, far too long. I probably remained more aware of her than of John Ritter for a good period of time for all my single data point is worth.
All I remember about that show was the shaking superimposed ocean that threatened to destroy the roller coaster apparently built two feet from the breakers at the end of the opening credits. Even at the time it was shockingly poor F/X. I’m not even sure what the point was - why not just pan out normally? Why add that awful effect? Who cares how close it was to the ocean? Why do I still remember this? So many questions.
Speaking of…
Step by Step
Most: Patrick Duffy perhaps out of the core cast for recognizable roles? Christine Lakin has a bunch of work, mainly one offs and voice acting. I’d edge it out towards Duffy for steady recurring roles. Jason Marsden was in 53/160 episodes but deserves honorable mention credit for a very full resume as well.
Least: A couple kids ended their acting careers with the show: Brandon Call, Christopher Castile and Josh Byrne