What games express sheer joy?

[Valkyrie-Favor]

Riiiiiidge racer, if your idea of happiness is gorgeous sunsets, bad techno, Reiko Nagase and constant screeching.

Mine is.

[foxhound1022]

For me, I think that it comes more in the form of unexpected events that happen in-game.

The other day I was playing Road Rash 64, and one of the CPU bikers got taken out by a car. The resulting hit rocketed his motorcycle into the head of another biker, who then wrecked, got run over, and propelled another biker in the air helplessly into a stop sign. I lol'd for a minute straight.

Also when you easily vanquish a boss character who is normally a bitch-and-a-half in a fighting game.

As far as just insanely silly, fun games: Three Dirty Dwarves comes to mind.

[Key-Glyph]

TMNT: Hyperstone Heist. There are so many variations on kicks, jumps, and slides that playing the game becomes a fancy choreographing experience, which I find exhilaratingly fun. This is hard to explain, but I like adding touches to my gameplay that make it more movie-like, when possible: making Sonic and Tails look upwards at the Death Egg as it rises out of the clouds, deliberately cutting maneuvers as close as possible in the Lion King's stampede stage, etcetera. So there's really nothing more satisfying than disposing of foot soldiers in the most complicated, acrobatic ways possible.

Fable II is another one, but in a different way. It makes me feel good just to be there in that universe. The music so so beautiful, the scenery is breathtaking --- and this is from a person who usually doesn't care about realistic graphics. I just want to live there, particularly in Oakfield; it reminds me of my childhood. And somehow the game comes together into a bigger artistic expression and experience than repetitive fetch quests (even though that's basically what it is, when it comes down to it). It's soothing and I was surprised by how attached I got to random NPCs and how moved I was by my own character's progression through adulthood.

I second Katamari, particularly any level in We <3 Katamari with this song playing in the background.

You know, I'm not sure if I answered the OP's question right. But both Hyperstone Heist and Fable II inspire a happiness in me that is much more than the basic "I am enjoying playing this game," which I think is what we're getting at. ...right?

[pankakes123]

The first game that comes to mind for me is the Kirby series.
Return to Dreamland had me smiling start to finish

This.

[AppleQueso]

I second Katamari, particularly any level in We <3 Katamari with this song playing in the background.

Man, EVERY song in the Katamari games is amazing.

[Damm64]

DCK 2
Maybe it's just the nostalgia but every time i play this game and listen this music:
http://www.youtube.com/watch?v=PwyipDW-t4Q
And THAT INTRO... EPIC!
http://www.youtube.com/watch?v=g7J8Tf6mreQ
When i play i just smile and everything it's better...

[8bit]

Some games that don't have violence at all and have a great attitude and gameplay are...

Bust a move series
Tetris
Flower
Parappa series
Frequency
Cut the rope
Wii Sports

Basically ots of puzzle and music games that keep the action fun and clean. Without a complete G rating I'd personally add...

Super Mario Bros 3
Mario Galaxy
Klonoa
Nights into Dreams
And many more colorful classics

[flojocabron]

The Rhythm Heaven series for both DS and Wii

[Menegrothx]

the Secret of Monkey Island

Yeah, you cant go wrong with Monkey Island. Sam and Max and other highly humorous Lucas Arts adventure games are also great but they arent always so innocent and colorful as OP wants They are more about sarcastic&witty remarks and black humor.
Monkey Island 3 might fit the bill, it's very colorful and cartooney, more so than MI 1&2.

[Erik_Twice]

. I'd add [...] Elite Beat Agents for similar reasons.

Right on! The passion is amazingly captured in all three Ouendan games and it really makes everything fun and beliable. And it makes the sad songs ultra-effective.

OutRun very joyful too but it's also about sharing the joy with those who are important to you.