Unreal never did it for me in the way, say, Quake 2 did, but it certainly looked gorgeous. Volumetric fog, wide-open spaces, and very high-detail enemies all contributed to that. If I'd had a PC with more muscle, maybe I would've enjoyed it more.
Not sure how we're calling generational splits, but Half-Life was based, at least originally, on the Quake engine and is superior to Unreal (and everything else that came before it) in almost every respect. So, no, not the best single player FPS of its generation.