Sure X8 looks bad, but that shouldn't be a major detractor if the gameplay's fine.
Not only do I disagree with that statement somewhat, I wouldn't say X8 gameplay is fine. The game just aims at being annoying instead of fun. It's always one gimmick or another. The vehicle stages (especially the city chase) are downright terrible and kill any of the appeal the game has, and they even take up 1/5th of the entire game because it's that short.
but sprites tend to take a longer time than 3-D models. well, thats what I heard. I mean, if it was remade drawn sprites for X8 that looked like the ones from CVS Chaos or from SF3 3rd Strike (actually, that would have pwned hard), that would take some time to get down.
Not only they may be harder to make but I had a theory. Gaming involves 3D staff/designers... so making 2D games is just a big hassle now. (and maybe the 3D staff is against it)
Anyway if I do say so myself, SF3 is the best looking 2D game ever. You're right, it would have been so lucky to get a Megaman game with that kind of quality 2D.
An observation I recently made was that Street Fighter 3 was made in 1997. As if that isn't incredible enough, it was actually made a number of months before Megaman X4 and only couple of months after Megaman 8. (both of which have the best 2D animation in any Megaman game)
I realize now, those were truly Capcom's glory days.