SOCOM 4: US Navy Seals.

Aliens Colonial Marines lol nuff said lmaooo

Buying a Gamecube a month before Windwaker and ended up disliking Wind Waker (i like it now though)

and an Xbox 360 at launch. I ended up only having like 5 games the whole gen

As a kid...a lot of stupid shit which I got rid off, but all of them were my parent's money so I really don't cry about it. 

As an adult with my own money....nothing really, I'm extremely picky with the stuff I buy, if I buy something I know I will like it, a couple of disappointments like Super Paper Mario and Metroid Other M, but I don't consider them terrible gaming purchase since I enjoyed both games to a degree in the end.

Soul Calibur V and Street Figther IV. I got both games at launch for $60 and probably spent a total of 5 hours playing both combined. Why?

I was a fan of EX-series SF and just couldn't appreciate SF4. Just not my cup of tea. As for SC5, the game seemed like a really stripped down version of SCIV with half the moves taken out, no weapon abilities, etc, and they added a damn bar like it was street fighter. Waste of a series IMO.

I feel like there's a lot of games based on licenced properties that I regret purchasing now.

Lord of the Rings: Fellowship of the Ring (GBA): This game came out during the same time frame as the Peter Jackson movies, and I guess it was supposed to be based off the books rather than the recent movies. What a hunk of crap. The combat was awful, the music was boring, the pacing was bad, and there was even a game-breaking glitch that kept you from beating the game. Ugh.

Star Wars: Attack of the Clones (GBA): I beat this game in like an hour. $30.

A lot of Naruto games: I used to be a huge fan of the manga/anime series, and got way too many games based on the franchise. Most were pretty subpar on their own, but I think being a fan of the series made me blind to that fact. Now that I've given up on the manga and have no interest in the series, I have no intention of ever playing any of those games again.

Now that I'm an adult, I really don't buy games unless I'm sure it's something I'm interested in. I do regret Sonic Lost World a bit, but I don't feel right including it with the crap I listed above. At least Lost World has high points...here and there....

PS Vita
Never have I had a system where I literally kept the thing in it's case for over 7 months. Still to this day, I'm stockpiling games, so I can always play something new and never worry about a dry spell. Right now it's Sly Collection and P4G. Also, basically no 1st party support.

I played Kinect a few times at a friends place and decided to get it. Haven't even opened some of the games I got with it. I did enjoy a few games on it though like Kinect Sports and Fruit Ninja, but I kind of regret getting it... because I feel I contributed to Microsoft doubling-down on Kinect as a way to market/sell the XBO.

Imagine how much better XBO would be today if they hadn't wasted their energy/focus on Kinect rehashes and failings.

I'd say my biggest regret was getting arma two for dayz. Arma is one of the worst games I've ever played. It has horrible controls, and you almost never run into enemies. Worst $7 I've ever spent.