I like Hybrid Theory the most. In fact, as soon as I heard it I knew it was the single greatest thing I'd ever heard in my life, and probably would ever hear. My problem with Meteora (I do still love it), is that it sounds washed out. I know, I know, there are some great moments (this is Linkin Park, here), but it really has an overall feel of... being too fine-tuned. Hybrid Theory is raw, and that makes it much better in my book.
To be honest its extremely difficult to choose but in the end I think I'll go for Hybrid theory because of its better song lyrics ... However meteora follows closely ... theres not a big gap between the two ... both are great albums.