Are those games anywhere near as big as Skyrim? Or do they have nearly as much content? And if you ask me, Skyrims combat is great. I enjoy it quite a bit. I even stopped playing AC3 to goback for Skyrim.
Size and content are irrelevant; the same system is used throughout the game, not like they have to change the system for every dungeon. If what you're saying is that Skyrim's size and content compensates for it's bad combat then I agree to an extent; that's why I play the game.
I like RPGs that have good combat, but combat can only hold the game up for so long before it all comes crashing down in a pile of [censored].
Obviously, combat is not the only thing an RPG needs. However crappy combat makes it unplayable (reason why I quit Oblivion; Skyrim combat is bearable, and not bad to the point where the game isn't fun).