People are choosing games like Banjo or Lost Odyssey (or even the guy who said he played Zelda at age 5), I don't know about you but....at age 5, I could barely read!
I got a NES with Mario/Duck Hunt/Track Meet for my 5th birthday. The mat broke almost right away so we exchanged it for Mario/Duck Hunt and got Zelda separate.
I never said I beat the game, and don't expect a 5yo to beat the game, but they should be able to play and enjoy it and when he gets older he'll be able to beat it.
Heck, my 1y.o. son can assemble Duplo blocks (the larger Lego blocks) granted he can't build anything interesting but he loves to stack them and carry them around. Sure it is too old for his age (really for 1.5-2 yo kids), but he still enjoys it.