I must ask: did the person’s name begin with a “D” and end with an “N”?
Cedar Point all the way. Something like 6000* rollercoasters all crammed onto this little peninsula in Lake Erie.
If you really want a blast from the past, I vote for Knoebels in central PA. No admission, free parking, birch beer, pierogies, a dark ride, and pickles on a stick. Plus, The Phoenixis a pretty cool little coaster.
*possible exaggeration
What the theme of Cedar Point, again?
Big ass rollercoasters…and Camp Snoopy.
Really, I (incorrectly, as I’m sure you’ll be only too happy to point out) mostly use the terms “theme park” and “amusement park” interchangeably. Yes, I know the difference; knew it, in fact, long before I ever started this thread. My goal was to get a general consensus of my fellow Dopers’ favorite theme/amusement/fun parks; my goal was not to start a thread and then go about correcting people in an über-persnickety fashion whenever someone interchanged the terms. But it seems that others can’t help but to be persnickety. Let me be clear: as far as I’M concerned, Cedar Point, Six Flags, Kennywood Park, hell, the two-bit, fly-by-night carnival around the corner from my house… they’re all legitimate fucking answers for the purposes of this thread.
Well, that changes things – favorite amusement park, without a doubt, is Knoebels.
If I rubbed a lamp and a genie came out and told me he could transport me to any theme park anywhere in the world for a day, I’d yell “Epcot!” without even thinking - so that’s what I voted for.
But I’ll put in a word for two of my other favorites, all of which are on the eastern side of the Big Pond so North American Dopers won’t be as familiar with them…
The original Legoland in Billund, Denmark. This is a theme park that really is all about the theme. The rides aren’t exactly amazing but I could spend days just wandering around.
Disneyland Park in Paris. (They seem to have finally decided on the name of this park! I swear we were there once when different official sources were calling it “Disneyland” and “Magic Kingdom”.) I haven’t been to Walt Disney Studios Park, so I can’t comment on that - and from what I’ve heard I’m not missing much, though I did miss the animatronic Chef Remy by not knowing it was there when we were in Paris, darn it! I also haven’t been to the original Disneyland in California so I can’t compare. But Disneyland Park in Paris is better in so many ways than the Magic Kingdom in Orlando. This is not to complain about MK, but to praise DP.
Also in Paris, Parc Astérix. Admittedly to get into this you need to know a little about the world of the Astérix comics, but still: this is as close as you can get to their world without breaking any of the laws of physics. It’s offbeat, zany, fun. If you think the French are all snobs who don’t know how to laugh, this park will disabuse you of that notion - and get you soaking wet in the process. They also serve wild boar burgers.
I love how every amusement park has some frontier-land area, where the log flume, tintype photographs, and giant barbecued turkey legs are. Even Busch Gardens in Williamsburg (theme: the least ethnic parts of Europe) has a ‘New France’ area so they can have their tintypes and log flume.
Oh, yes. I’ve seen pics of DP (formerly EuroDisney), and the architecture and landscaping are unmatched by anything I’ve seen at any of the other Disney parks. And that’s saying something! Would love to go for a day when I’m next in the region.
Universal. At least until they got rid of the BTTF ride lol. Really felt like you were traveling back in time in a flying DeLorean, or being attacked by a giant ape, or trapped in an earthquake, or buffeted by a tornado, or shot at by Cylons…
It is and I do. You wanna make somethin’ of it??? 
“Roller coasters” is the only theme worth beans. Everything else is just flashy facades, screaming children, and overpriced snacks. My ideal theme park is one where you give them a heap of money at the front and they just inject you with caffeine and various other stimulants and shove you directly into a non-stop chain of acceleration-oriented thrill rides that culminates in a rocket-powered parabola to the stratosphere with a freefall splashdown in Lake Michigan.
So yeah, I came in to mention Cedar Point too.
One of the authors is a member here (Len Testa).
Epcot, for drinking around the world. Seeing the Americanized take on all the countries while chatting with cute women and being slightly buzzed - 10 thumbs up.