I just never got into Buffy - I not a big Vampire/horror fan so it didn't appeal to me.
I've like all of Kevin Smith's comics - Green Arrow is a notch behind Daredevil. The current Batman comic isn't bad either.
LoEG is awesome. The movie was horrible because they changed so much of the content, like adding Tom Sawyer (who was added because the studio execs thought that American audiences wouldn't like the film because there was no American characters - even though Sawyer is from a different time period than the rest).
I highly recommend the Ultimates - it's unlike any super hero comic I've read. Volume 2 was good, but not at the level of the first. Millar's War Heroes (I think that's the title) hits on some of idead he had for the Ultimates and didn't use.