That is one freaky Mario avatar you have there.

I haven't played MP3, I hear it is excellent, but Mario Kart will last ages, in the past 2.5 months I think it has caught up with the other two games I had played to death, LoZ:TP and RE4:Wii (both around 180 hours)

Welcome to the site, get MK.

The problem with Mario Kart is - once you buy it, it is unlikely you'll play any other game for at least a month.

Hard one there. Did you like the other prime games? Other metroid games? If so then get prime 3 because it's an amazing metroid game for the fan. If not so much get mario kart, because most people aren't hardcore enough for metroid.

Have you played the previous Metroid installations? Personally, I'd get Prime. It's so amazing. I've played Mario Kart and it's really fun. The online is great, too. It all comes down to what you're looking for: a single player experience or multiplayer experience.

MKWii would probably be the longlasting game. It has excellent online play and you will be addicted to it-guarenteed!

Welcome to VGChartz! Enjoy it here!

Definitely get MP3. The gameplay in MKW doesnt even come close to the gameplay MP3. While you might play MKW for a little bit longer the better game is definitely MP3

Metroid

It really doesn't matter which one you pick, since they are both stellar games.
MK is great for the online and multiplayer. It is also a great game for quick 15 minute games.
MP3 is epic and full of great visuals and excellent puzzles. Whenever I played it, I had to set aside at least an hour at a time. Usually 2 or 3 hours.
If not now, eventually you MUST buy both.

BOTH!! I prefered MP3 besides MK but that ain't mean that i won't get MK :)