Kirby adventure green greens
the opening music to Banjo Tooie
Ch.7 Music of Paper Mario...

Got to be these 3 classics from Streets of rage 2

 http://www.youtube.com/watch?v=byBGbcoFrn4#

http://www.youtube.com/watch?v=5MI2fpmKFx8#

http://www.youtube.com/watch?v=aELhHGUEhz0#

Still Alive from Portal is very, very catchy.

"Nin-Ten-Do It's a cereal...Wow!"

Ok, that may not be in a video game, but it has certain been stuck in my head for a couple decades now.

In seriousness, I'd have to say the Super Mario Brothers theme as well.

OK, let's all agree with the Mario theme, but which version of it? From the NES, Super Mario All-Stars, the GBA games?

Doesn't matter, all of them are just as catchy. It's a toss up.

Mario bros theme, hands down.

Donkey Kong Country theme

Super Mario Bros. theme is the most recognisable, AND very catchy, but not the catchiest.

The catchiest song is a tie between A-Type Music from Tetris and the classic Saria's Song from Ocarina of Time.
I quess they are really even. If you'd force me to pick one of them, my brains would explode out of impossibleness.

@ Hawk: That song's in my brain forever, too... such an awful(ly catchy) jingle...

There are tons of video game songs I prefer, but I must admit that I find the new SSBB theme really, really catchy. I hum it without realizing it.

It doesn't help that there are about 300 variations on the song in the game itself, and then when I found the youtube videos putting "misheard lyrics" to the tune, it was over.

Omelet prevail!