thing1 : I never played that game. I am not really a big NBA fan, but the games can be fun to play.

EDIT: Misread your post.

tgags123 : I said NFL, as in football, not NBA, as in basketball...

It's not so much that the games I've chosen are hated or under appreciated, they just aren't known enough.
Anyway, all the games I chose can actually be found right in the RGR around the corner.
1. Mystical Ninja Starring Goemon- It's a good 3-D platformer with a really bizarre story set up and some really cool gameplay ideas. It's pretty amusing at times, and it's heavily steeped in Japanese Mythology. It's got some blemishes here and there, but it's still pretty fun.
2. Goemon's Great Adventure- Sort of similar to the game I just mentioned, but instead it's a 2D platformer. Not only that, but it has full on Co-op and Giant Robot fights after every boss that make your inner 8 year old grin. It's definitely shorter, though.
3. Klonoa: Door to Phantomile- It's a 2D platformer similar to Goemon's Great Adventure (In more ways than one), but it takes itself a tab more seriously and is just as good a choice, even without the giant robot fights.

I feel as if shadow the hedgehog for the GameCube is underrated. I love the game, but it seems as if not many people even know about it.

I think Donkey Kong 64 was another highly under rated game. Sure, it may have been a knock off of Super Mario 64, but it was the first Donkey Kong game that wasn't an arcade game, or a side scroller ( at least to my knowledge ) . 

And the amount of things to do in that game were... way to many to count. 

I consider Dynasty Warriors an underrated games. Going around as one man destroying an entire army by yourself. I always found it to be an amazing game. The one most underrated was the online version from aeria games. They shut it down in January of this year telling everybody sorry but games don't last forever. 

Cubivore, Chibi Robot, E.V.O. Search for Eden, ZombiU,  pikmin (all of them), 007 Everything or nothing... 

Under rated game? Wikipedia. But that is not a game! It is a wiki! Nope, its an MMORPG, and here the proof straight from Wikipedia: http://en.wikipedia.org/wiki/Wikipedia:Wikipedia_is_a_MMORPG .

All joking aside, OMG THE RED RINGS, a hack of Sonic 1, it may be hard, but it is fun to try to figure out how the [censorship!] to get past (or around) a patch of deadly bouncing red rings, but unfortunately some levels are impossible.