One of the things I value in a game is cuteness. Looking lifelike is great, but I want a game with its own style and I prefer that style to have some cute things in it.
Kirby's Epic Yarn
Sure, you might feel like a 5-year-old playing this game, thanks to a cheesy narrator, but the fabric textures and whimsical creatures put this in my top five cutest games. Even the sound effects are cute.
Little Big Planet 1 & 2
Not only is your character basically a knit stuffed animal, but you can make him have expressions and dress him (or her, I guess?) up in more cute clothes. Personally I think there should be more games where you can dress up and then do awesome platforming, or shooting or whatever.
A boy with a magic notebook conjures up anything he can write down. The cartoony style is consistent throughout the game, and even scary things like witches, dragons, and the devil take on an aura of cuteness. It makes sense that they'd be somewhat helpless, given that you can throw away things you make at any time.
Katamari Damacy franchise
You know this game... go around rolling small things up into your Katamari (or "clump") so you can roll up even bigger things, even the moon, even the universe! Part of the charm is that every object has a name, and your prince avatar has a bunch of cousins you can trade places with.
This rhythm game is adorable. I picked up the DS version in Japan and my only regret is not also buying the Wii version (which has multiplayer and mini-games). How did they make a taiko drum so cute? The Japanese voice clips sound like a little drum just dying to play, but somehow it just sounds cheesy in English.
I don't think Animal Crossing and Nintendogs are all that cute. Certain Pokemon are very cute, but inevitably grow into something ugly (Scraggy, for example, is immensly cute, and the grows into some punk with a mohawk). Other cute games I considered (thanks, Casual Girl Gamer): Costume Quest, Glitch, GameDevStory, all the Grow games, LevelUp, Little Wheel, Home Sheep Home, and Sissy's Magical Ponycorn Adventure, and World of Goo. Mechinarium is definitely artistic, and I think it has some cute points too. I hear that 3d Dot Game Heroes, Cut the Rope, and Obaku are pretty cute, but I haven't played them yet. What game do you think is the cutest?