The games I own:
Metal Slug Anthology - You can find this on eBay/Half/whatever for $20. I don't even know if it is available new but at that price, you need to get it. Includes Metal Slug 1-6. A few different control setups. The controls are the greatest flaw. They are good, not great. The worst involves shaking the controller like a tard to launch grenades. I believe you can use the GC controller but I wouldn't buy a Wavebird for this game if you don't own one already.
Super Mario Galaxy - This game is 1000x better than that abortion known as Super Mario Sunshine. It is like Nintendo realized how badly they fucked up with the franchise and came to redeem itself. All is forgiven. Not the best Mario game in the series but it is a very good one and has enough challenge to not make it a pushover like Mario 64.
Super Smash Bros. Brawl - I got this because I drowned in the jizz of overactive GAFfers who claimed it to be "Game of the Forever." That phrase is lame as fuck and so is Brawl. If you want to buy Brawl, you better make sure you have roommates or friends or whatever that like the game. It is essentially Melee with more shit. If you hated Melee, keep away from Brawl. It is not a complex fighter. It is a mascot party game. You need friends because the online mode is so broken that you might not find much luck in immediately connecting online and finding others to play without a laundry list of problems. Nintendo claimed to want to wait until they got online gaming down pat before having it in their games. They lied as always, lazy fucks.
Mario Kart Wii - I still think the DS version is much better. The wheel sucks and is a novelty. Once you get the golden wheel (race online a few times), the novelty becomes useless. It takes the Brawl route in throwing in a bunch of characters. Unlike Brawl, MKWii introduces a bunch of useless fucking characters and snubs several good ones that should have been used instead. The new courses seem like MKDS rejects but not Double Dash terrible. Online is decent and you can actually play a few games without Nintendo's shitty servers kicking you off.