it is
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BG2 is not that content-rich. The ES games and Witcher are much, much longer games when played to completion
I love BG2, but some people here are exaggerating quite a bit
I take offense at the term "archaic gameplay", though. I recently finished Witcher 3 and DLC, which some people seem to think of as the new king of RPGs. The game is excellent in some ways (the DLC linear story segments in particular, ironically), but the combat and ability system is extremely simplistic and barely allows any room for customization. It's nice that they wrote a short journal paragraph for each and every throwaway quest, but the game world is filled with absolutely mindless tasks of the likes that you usually find in MMOs. That really dampered my enthusiasm for the game after some time - games developers still don't know how to populate these massive game worlds with meaningful content
BG2 is a tactics game in combat. Encounter against filler enemy groups are thankfully resolved in mere seconds due to increased game speed + boots of haste + real time combat, tough enemies can take a long time and a number of reloads and you will pause constantly to micro-manage your team member's every actions. It's a good system and hasn't really aged much at all. Not even Pillars managed to reach it's heights due to various factors, such as uninspired encounter design
the thing with BG2 is that is has a good story and writing, but not the best in the genre, good companions and sidequests, but some other games might have outdone it in one aspect or another. It's just an all around competent game with a timeless combat system, and used to be the top RPG for a long time, or might even still be