More Hitchcock, I don't have any of his films even though I am a big fan
More foreign films
More older films (pre 1980)
More Anime
More comedies

though I work out every day new plans to improve my DVD collection ... what I really need is more time to enjoy my actual collection. Silent movies, I want silent movies mainly, then I need 30's and 40's movies but most of the titles on my list haven't made it on DVD still. Until now I've tried to fill gaps and 2003 has been a good year: Resnais, Leone, Kurosawa, Bergman are some of the beloved names I missed.
btw: I think everyone of us could improve the collection erasing titles more than adding new ones that's why I always say: a good collector needs to be patient.

My Collection

DVDs with full storyboards.

I have:

True Romance (Best movie AS a DVD, in my limited opinion)
Fight Club

Getting:

Fear and Loathing (as soon as my roommate decides whether or not to sell his extra to me or his other friend). I know the storyboards are not complete (or even completely readable), but its better than nothing. Good movie, as well.

More Classics. I am about to put plenty of them on my Xmas list.

Foreign Films by far.... I've been renting (doing some sampling based on various reviews) some of them to see if I like them and for some reason I just can't get into the Italian, French, German or Russian Directors. I've got a decent collection of Japanese movies (mainly Kurosawa, Masumura, Masume, Kadokawa and Inagaki... I'm working on Yasuda at the present), but I just can't seem to get into any other nationality's directors....

I rented The Bicycle Thief, 8 1/2, and Cinema Paradiso lately and either I didn't like their directing style or I felt they were uninspiring (nothing extraordinary that would prompt me to buy tem) I just couldn't get into them... which is funny because it's not even the language barrier (I speak Italian).

In fact, I would appreciate any recommendations from some of the big foreign film collectors out there.

Short Films....maybe my attention span is getting shorter with my advancing years
But in all honesty i'm a sucker for those collections of independant 'shorts' etc. and the more i own the merrier!

More foreign (aka Criterion).

I need more Criterion too! 35 are entirely too few!

You didn't mention Bergman. Do you have some of his work or have you seen any of his films? If you haven't, I think "The Seventh Seal" is the perfect start.

season sets of shows Like Star Trek, Babylon 5, Simpsons, Futurama.

I dont have any of them at the moment and the star trek ones are so expensive.

improving? none. but i lack many genres - criterion, classics, horror, musicals, etc...but i dont want them anyways.

I need more comedies, although I dont find the replay value of Comedies near as good as Action or Drama, which is why i dont buy as many. God Bless Old School for being every bit as funny each time I watch it as the first time though

Musicals and Shakespeare

But, honestly, it's not for lack of trying. I'm a "special features" fan (especially for older movies where I wasn't around to know a lot about them when they were released), and the studios aren't doing a great job with these. It just kills me that there are no extras in the Rodgers & Hammerstein Collection (not to mention that Flower Drum Song isn't even in it). But I must say that the Sound Of Music, West Side Story, Fiddler On The Roof, and Seven Brides For Seven Brothers releases were all handled very well (probably why I have them ).

Storage. Easily the thing that I need to fix the most.

I'd like to fill in the gaps in my Criterion Collection titles. Gotta catch 'em all!

Then I'd say more Bollywood, more silent films, and more stupid teen-hijinx comedies. I don't have too many of those.