MarkB
Legend
I know I picked up the BG series simply because it was a D&D game using the 2nd edition ruleset. I still play through the infinity engine games because it's the only way to get an AD&D fix on the computer. The gold box games are a bit dated and I'm too spoiled by modern interfaces. The forgotten realms logo didn't make a bit of difference. It was AD&D! on the computer again finally! That's all that mattered.
Indeed - I originally bought Baldur's Gate because I'd played D&D in school in my youth, and wanted an RPG that used that ruleset. I enjoyed the game and its sequel so much that when Bioware were developing Neverwinter Nights, I joined the development forums and actually bought the 3e rulebooks purely in order to participate in the discussions.
And having bought and read the rulebooks, I was inspired to finally seek out local RPG clubs and get back into playing tabletop RPGs. So not only do I directly relate the games to the D&D setting, I consider them responsible for me getting back into D&D after a 15-year break, re-introducing me to what has since become my favourite pastime.