abbayarra: They may not be the masterpiece that baldur's gate 2 is but it is not far behind and a wonderful effort for a small independent firm like spiderweb.
This is all opinion of course, but personally I think the Avernum and Ultima series are both better than the Baldur's Gate series. Two reasons:
1) BG mainly delivers its story through a handful of major "turning point" moments -- big, sweeping cutscenes or major dialogues. However, they're also nonlinear. As a result, most of the time the player isn't really participating in the main story. I constantly felt like I was losing all immersion in the plot every time I went to do something else. In Avernum and Ultima, on the other hand, the story is delivered constantly through little details, so the immersion never breaks (even though they're also nonlinear).
2) The difficulty/leveling curve is a lot steeper in BG than it is in Avernum/Ultima. This means that as you progress nonlinearly and gain levels in BG, you become super powerful, and most of the fights that you haven't done yet become super easy (except for a few boss fights where the difficulty jumps tremendously compared to everything else, which I also don't like). The Avernum and Ultima games that I've played have shallower curves, so you can explore to your heart's content and still feel like you can get a decent challenge almost anywhere you go. To be fair, BG1 also did a pretty good job of this due to the low level cap. It drives me crazy in BG2 though.
Obviously BG is great too. This is just my 2 cents for people interested in trying out the older RPGs.