Actually, it's been shown many times thats 2D backgrounds are less detailed
. Lower displayable resolution, static environment, and in the case of BG and BG2, rather dull, pastel looking backgrounds. A 3D enviroment would actually allow for more detail to go into the background, making it interactable, and good looking.
Simply put, a connection between poor gameplay and 3D graphics can't be made effectively, simply because 3D is still a growing method of gaming graphics. Hell, if anything, we should hate 2D more for the reasons I've been seeing in these threads, you know, seeing as there are far more horrible 2D games, then 3D games...
Oh, and Baldur's Gate 2, I hate to say it, it's never going to be repeated. You have to understand that. To think that BG3 will be on par, or better, is silly, simply because of the all the already gathered hype, high expectations, and people analyzing this 2D vs. 3D argument to death. But, it's not going to be the graphics of BG3 that dissapoint, I can almost assure you of that.