I've spent many hours and enjoyed the Mario games of old (SMB 1, 2, 3 and 4) back in the day. To say that I've played them to death is no understatement, and given that I'm not too crazy about Mario games in 3D, I'd have to say that I'm not a fan of the new Mario games and the character in general. I think Nintendo really began to separate their core audience when they gave Mario a voice in Mario64 (It's a meee, Mario---ugh...I shudder everytime I hear his fruity voice in the last few games).
For me, I simply associate the older games as fun kiddie games since I was a kid when they first came out. Mario was a lovable, somewhat generic character (with an evil past...who can forget his role in Donkey Kong Jr!) back in the day but he certainly has not aged well or evolved enough to stand the test of time today.
I'll gladly play the older games on their native formats over the newly rehashed GBA cash runs, simply out of sheer nostalgia and some relatively brilliant game design. But overall, I think Mario has had his day and is becoming played out and made out to be too childish in this modern mainstream era.