One of the best, but no one talks enough about him.
I'll give you some starting points.
Double Indemnity (http://www.toonzone.net/forums/showthread.php?t=278448)
Sunset Boulevard (http://www.toonzone.net/forums/showthread.php?t=278475)
Some Like It Hot (http://www.toonzone.net/forums/showthread.php?t=278505)
The Apartment (http://www.toonzone.net/forums/showthread.php?t=278529)
I want very much to see Double Indemnity. I'm only acquainted with Sunset Boulevard, and I never liked it much. It's not as dark as I like it and I'm not the hugest fan of the man (and he's an excessively boring character who I wish wouldn't talk so much) being the messenger of all the cynical observations. If only he knew what a joke he was, then he'd be narrating a different tune.
I liked The Apartment because it has Angus in it early on in the movie.
I'm making another Wilder talkback tomorrow for an overlooked film of his airing on TCM on Wednesday. Look out for it. ;)
But yeah, he's one of my favorites. I think only Hitchcock might have had more classic Hollywood films than Wilder, but even Hitch didn't get to work with some of the talents he did, like Lemmon, Monroe, Hepburn, Bogie, and William Holden. Some of the best and most iconic actors of all time in some of the best and most iconic films of all time.
I love how his films can be cynical like in Double Indemnity and Ace in the Hole, gently be entirely about sex like in Some Like It Hot and The Seven Year Itch, blackly comic like Sunset Boulevard and One, Two, Three, inspiring and tragic like Stalag 17 and The Lost Weekend, and be all at once like in The Apartment.
Again, finding a filmmaker with as wide of a range of classics as these is hard to consider, and I'm only listing a handful of his classics.
Here's my other one that I promised. (http://www.toonzone.net/forums/showthread.php?t=278658)
It's funny, Irma used to be one of his more popular movies when it came out, but recent years haven't been too kind to it in terms of reception. I think it's a good movie, better than Some Like It Hot, and deserved a little more recognition.
But yeah, check it out, if you can.