You're not alone. BG1 has a quality about it that BG2 simply does not. It's not a clearly definable thing, and different people will tell you it's different things, and others will tell you that BG2 is far better, for other reasons, not least of which is the superior game engine of BG2. I have struggled to define for myself what it is that takes me back to BG1 more than BG2 -- I've heard all the usual reasons people give, and most of them are sensible reasons, but not one put's it's finger right on the button... it's an elusive thing (that's why I'm not going to even attempt to tell you what it is) that boils down to personal taste, I guess.
I feel like I have to grind more in BG2. And I feel like my character's epic-ness is not well-noticed. I have yet to get all the way through BG2 despite owning it since just after it came out. But BG1 has been on every computer I've ever owned after I played it (I played BG1 after playing BG2).
Nonetheless, there's tons of great moments in BG2 worth playing for. I'm a sucker for save-load cycles during crazy hard battles that I do to myself (like going after a high-level lich with new characters or taking out an early dragon).