YOSHI

Super Mario World

In this game, Yoshi's friends had all been captured by Bowser (as well as the Princess) and Yoshi went off to find them. Mario, by virtue of his sheer tenacity and a love for the aforementioned Princess, inadvertantly finds all the yoshis (red, yellow, blue and green) while searching for his arch-enemy. In this game Yoshi is at his cutest while hatching out of eggs and bouncing up and down waiting for Mario.

Yoshi's Island: Super Mario World 2

This game is the prequel to the first Super Mario World game and shows that Mario and Yoshi have known each other a long time. While the stork was carrying babies Mario and Luigi to their parents, the evil magikoopa, Kamek, kidnapped them but Mario fell among the yoshis and they decided to help the baby find his brother. So all of them carry the baby across their beleagured island (for Kamek sent all the Koopa Troopers in) to find Luigi. Yoshi is very cool in this game because his tongue is more of an accurate weapon than in the previous game. Oh, and he can fire eggs.
Artillery.

Tetris Attack

This game is a little like Dr Mario, in which you have to connect blocks of colours to eliminate them from the screen, but with Yoshi in the driving wheel. I believe (as I haven't played the game much myself) that the idea is that Yoshi plays his friends at the game to free them, and then plays against the bad guys to destroy them (these friends and bad guys being the Nintendo). It isn't as Yoshi-y as some of the other games, but Yoshi is in it so it had to be mentioned, really.

Mario64

A cunning cameo in this one he has, but surely the highlight of the game is the secret rendezvous with the original green dinosaur himself. It's just a shame he vanishes afterwards. I don't like the 3D graphics on Yoshi all that much -- he seems to lose something, although he is still excellent.

MarioKart & MarioKart64

I won't start talking about the actual game or I'll be here all day because I love it, but suffice it to say Yoshi is in both of them and not at all bad, either. Not tough, not weak, he's great. But I would say that really. Okay, so he looks a little odd in the sitting position, but who cares when you're burning round the track and amusing yourself with killer banana trails? For that matter, I think that applies to all the Kartists in the game.

Yoshi's Story

This game is far too happy. The trees are happy, the flowers are happy, the eggs are happy... even the shy guys are happy until you steal their fruit! But excessive happiness aside, this game makes Yoshi so cute it's almost sickening. The plot is that Baby Bowser, no doubt fresh from his defeat at the hands of Yoshi in Super Mario World 2 has kidnapped the Super Happy Tree and turned the yoshi's world into the pages of a storybook. The yoshis are babies and intolerably sweet as they sing, bounce, jump and eat themselves towards a new peak of joy -- the Super Happy Tree! To be honest, no matter how cute the yoshi's are, I think they'll explode and my mind will fry if they get any happier.