I wouldn't write off either Tales or especially Tekken as obscure. Hell, my current avatar is Eddy Gordo, a character FROM Tekken. Tales has more games on Nintendo systems, so that likely has to do with how many Smash fans, who might only play games on Nintendo systems view Tales in a higher regard than Tekken. In general, it's a fairly big JRPG series.
Tekken's a Top 5 fighting game franchise and, while not to the extent of Tales, has had a few Nintendo releases, Tag 2, Tekken Advance, 3D Prime. It's also out-paced Virtua Fighter as the most iconic 3D fighting game, despite VF being where the sub-genre got it's start. So to say that Heihachi isn't an Iconic game character and arguably Jin and Kazuya, I would say is about as dumb, if not dumber than saying Terry's some nobody. I can admit my bias though, as I grew up with Tekken, even more so than Mario or Mega Man.
Heck, one of the boons to adding a Tekken character in my eyes is potentially getting more Nintendo fans, into a series I personally find to be fantastic. I'd be really happy if we ever got a Tekken collection too. But that's getting a little off-topic I suppose.