All very good games but mind that BG I was released in 1998, IWD two years later. I see some people playing BG I for the first time and then saying stuff like “it is quite dull compared to BGII” but when BG I was first released, I think it was the first isometric computer rpg (in a fantasy setting) ever of that scale (taking into consideration not just the story and the world for which there were probably precedents but also graphics, music, voice acting, npc interactions etc etc). There was fallout I that came out in 1997 (what a golden age for computer games!) but again that is a different context.

I remember the first time I played it as a kid (coming from table top rpgs), I might have peed a little from excitement seeing how detailed the game was. IWD I was more like a small scale repeat of BG I in a different context. So can’t really call that genre defining. Similar story with BG II and IWD II. BG II took style of BG I and built an even grander RPG with more detail in NPC interactions and the world. I don’t think one can even compare IWD II to BG II despite it being a very good game. I am not even sure there has been an isometric game of that scale for the like following 10-20 years after BG II.