From the IMDb:
My list (in chronological order):
The Sure Thing
Better Off Dead
Eight Men Out
Say Anything
The Grifters
Bullets Over Broadway
Grosse Pointe Blank
Being John Malkovich
High Fidelity
Huh. I could only come up with nine. But I haven’t seen 1408 yet.
Identity
Midnight in the Garden of Good and Evil
My ten:
Stand By Me
Grosse Pointe Blank
Midnight in the Garden of Good and Evil
Being John Malkovich
…
Hmm. I haven’t seen nearly as many of his movies as I thought I had.
Without having read anyone’s answers, here is my list:
The Sure Thing
Cradle Will Rock
Being John Malkovich
The Road to Wellville
Fat Man and Little Boy
Admitedly, I haven’t seen that many of his films.
I liked him in The Grifters (but not as much as Annette Benning - man, she’s smoking hot in that movied) and Grosse Pointe Blank. I didn’t like Being John Malkovich as much as I thought I would.
I’m a fan of Runaway Jury.
Other than that. . .
**High Fidelity
Say Anything
The Sure Thing
BJM
**
were great.
I saw GPB but it didn’t register with me.
A lot of his other stuff is just “good”. Some of it SUCKS.
High Fidelity (one of my all time top 10)
Grosse Pointe Blank
Being John Malkovich
Bullets over Broadway
Identity
1408 (I thought I’d hate this one)
Say Anything
Runaway Jury (underrated)
The Thin Red Line
Sixteen Candles
I’m sure we can eliminate The Road to Wellville. Of that much, I’m sure.
What? No America’s Sweethearts? No Serindipity? How is this possible??
I doubt his top 10 would match most viewers’ lists. He may have, say, had a life-changing experience on the set of The Thin Red Line and think the end result is a work of art. Still doesn’t mean I don’t find it dull as nails.
My list of favourites:
Eight Men Out
Say Anything…
The Grifters
Bullets Over Broadway
Grosse Pointe Blank
Being John Malkovich
High Fidelity
Stand by Me (not sure if he’d consider this a movie he ‘made’ or was simply a part of, considering the size of his role)
Midnight in the Garden of Good and Evil
The Journey of Natty Gann
It’s funny. Although I would have said I really like John, when I went to his IMDB entry I was surprised at just how many of his movies I haven’t seen.
Identity
High Fidelity
Being John Malkovich
Grosse Pointe Blank
The Grifters
Say Anything
The Sure Thing
He did good work in True Colors, but it wasn’t that great of a movie.
I’ll probably say that he thinks that his work in these movies was important:
Bullets Over Broadway
The Thin Red Line
Cradle Will Rock
Anyone could have played his part in Midnight in the Garden of Good and Evil, folks… that was Spacey’s movie through and through.
Moved from IMHO to CS.
He’s being snarky and self-deprecating. I think he just said 10 as a round number, not that he actually meant 10 exactly. If he stopped to look at the list I know he’d find more than 10.
My list of Cusack movies (though he wasn’t lead in all of them), in no particular order:
Bob Roberts
Grosse Pointe Blank
Broadcast News
The Sure Thing
Say Anything
Being John Malkovich
High Fidelity
The Grifters
Bullets Over Broadway
The Journey of Natty Gann
I’d also add to the list:
1408
Cradle Will Rock
I haven’t seen some of the ones mentioned, like Better Off Dead, Eight Men Out, Midnight in the Garden of Good and Evil and Identity.
I haven’t seen this either, but I’ll bet Max would be on the list.
Worst John Cusack movie: Must Love Dogs.
I thought it was going to be a can’t-miss romantic comedy. I think it’s the last movie I walked out on.
If you’re trying to guess his favorites, then you can strike Better Off Dead. I’ve seen it reported that he absolutely hates that movie.
I think it rocks, of course. 
I was intentionally excluding films in which he had only a peripheral role (like Bob Roberts, which I otherwise would have put on the list) as being outside the spirit of his pronouncement, but that’s open to interpretation.
Interesting that he hates Better Off Dead. I hadn’t heard that. I still use “Go that way really fast. If something gets in your way, turn” as words of advice.
The Ice Harvest
Better Off Dead
Eight Men Out
Say Anything
The Grifters
One Crazy Summer
Grosse Pointe Blank
Being John Malkovich
High Fidelity
By good, did he mean that he acted well in them or that the movie itself was good? 
He might be including the as-of-yet unreleased War, Inc., an unofficial sequel (or possibly prequel) to Grosse Pointe Blank. I saw a trailer online a few months ago and it looks great, although I haven’t heard a thing about it since.
The Ice Harvest (2005) … Charlie -> He was pretty good in this uneven movie.
Serendipity (2001) … Jonathan Trager .-> I like him and the movie was good
America’s Sweethearts (2001) … Eddie Thomas. ->Terrible movie, he was not good.
High Fidelity (2000) … Rob Gordon . ->Great Movie & Character.
Being John Malkovich (1999) … Craig Schwartz . ->Great Movie & Character.
Pushing Tin (1999) … Nick Falzone -> Silly movie, but I enjoyed it and he was the best actor in the movie.
The Thin Red Line (1998) … *Capt. Gaff -> aka Mince ligne rouge, La (Canada: French title) * -> I did not like the movie, he was fine in it.
Midnight in the Garden of Good and Evil (1997) … *John Kelso * -> Great movie and breat roll
Anastasia (1997) (voice) … *Dimitri * -> He did a good job in a middling animated movie.
Con Air (1997) … *U.S. Marshal Vince Larkin * -> Silly but fun movie, he was very good, second best character after Steve Buscemi
Grosse Pointe Blank (1997) … *Martin Q. Blank * -> Great movie and great role.
City Hall (1996) … *Deputy Mayor Kevin Calhoun * -> Good movie, he and Danny Aiello out actor scenery chewer Pacino.
The Road to Wellville (1994) … *Charles Ossining * -> He was very good in a movie where Anthony Hopkins was terrible and Dana Carvey was painful to watch and Matthew Broderick stunk.
Bullets Over Broadway (1994) … *David Shayne * -> He was good in a good movie.
Bob Roberts (1992) … *Cutting Edge Host * -> Small Part and he was good.
The Grifters (1990) … Roy Dillon -> He was great in this entertaining movie.
Fat Man and Little Boy (1989) … *Michael Merriman -> aka Shadow Makers (UK) * -> One of his best movie, one of his best roles.
Say Anything… (1989) … *Lloyd Dobler -> aka …Say Anything… (USA: promotional title) * -> His signature movie and he was great. Not my favorite John Cusack movie however.
Tapeheads (1988) … *Ivan Alexeev * -> Fun and strange movie, he was great.
Eight Men Out (1988) … *George ‘Buck’ Weaver * -> My second favorite John Cusack Movie. He was great.
Broadcast News (1987) (as John Cusak) … *Angry Messenger * -> Small Role, no comment.
Hot Pursuit (1987) … *Dan Bartlett -> aka Persecución intensa (Mexico) * -> Crappy movie, no camp value, he seemed to sleep walk through it. Must have just been a quick payday or something.
One Crazy Summer (1986) … *Hoops McCann * -> Fun and stupid movie that I was the right age for. I probably remember this too fondly as I saw it in the San Diego Drive in with about 20 friends and a few cases of beer.
Stand by Me (1986) … *Denny Lachance * -> Small role, he was very good.
The Journey of Natty Gann (1985) … *Harry * -> He was great in this little remembered movie.
Better Off Dead… (1985) … *Lane Meyer -> aka Better Off Dead (USA) * -> My absolute favorite John Cusack movie. I love this movie, one of my favorite 80’s comedies. (I want my two dollars!) (Ohhhh. Tentacles. N-T. )(This is pure snow! Do you have any idea what the street value of this mountain is?)(Now that’s a real shame when folks be throwin’ away a perfectly good white boy like that. )(Two brothers… One speaks no English, the other learned English from watching “The Wide World of Sports.” So you tell me… Which is better, speaking no English at all, or speaking Howard Cosell?) I don’t care if he doesn’t like it, I do. I rated this one a 10.
The Sure Thing (1985) … *Walter (Gib) Gibson * -> A good solid performance in a Rob Reiner little gem.
Grandview, U.S.A. (1984) … *Johnny Maine * -> Forgettable role in a forgettable movie.
Sixteen Candles (1984) … *Bryce * -> Small but competant early role.
Class (1983) … Roscoe Maibaum -> Small but competant early role.
So I have seen a lot of his movies and I like him in most of them and I like most of his movies.
Jim