Big picture perspective: He was the more requested character in the game, and a lot of people seem really happy about it, so it definitely seems like a win for Nintendo and a lot of fans.
My personal perspective: I was hoping Crash Bandicoot or Master Chief would have made the Smash roster at some point. Smash has evolved into this sort of museum of video game history, and now that it's going in that direction, there are some blindspots. It feels a bit odd that they embrace certain third party characters (Sonic, Snake, Cloud, etc) while ignoring some of the other obvious ones. I understand Halo hasn't appeared on a Nintendo console which may be their technicality for disqualifying it, but nevertheless.