I generally try not to compare things, one vs the other.
For me, BG1 and BG2 are among my most beloved games. I have played both of them more times than I care to admit. It is safe to say that I have put more hours into BG series than any other single game, and likely any other franchise. So that is an incredibly high bar.
Thus far, I have thoroughly enjoyed BG3 in early access. I think it has a ton of potential to rank up there in my estimation. I love the graphics, the turn based combat, the companions, the story, the (more or less) open world approach to tackling the map (meaning that you aren't restricted to a single path and can go anywhere you don't get killed. might be a different definition than others' of 'Open World' but it is what I meant here). I love the exploration and the different ways to tackle various challenges. My latest playthrough was with a bard and I am silver tongue talking my way out of most things. So there is definitely versatility.
In the end, I look forward to the full release and thoroughly exploring the entire game before I make any judgements. If the rest of the game lives up to Chapter 1, it is likely to make it into my top 10 list. I guess we will see with time.
