What makes a game good (to me) is when I enjoy it.

As for what makes me enjoy a game, there's just so many different answers to that question, and there's no way I can come up with a universal rule to what makes a game enjoyable.

For example, an RPG like Bahamut Lagoon with a really deep story, lots of customization with teams and dragons, and a really strong emotion inducing soundtrack is really enjoyable to me.

Yet, a platforming game like New Super Mario Bros. Wii has none of those things (the soundtrack is still enjoyable, but it doesn't evoke emotion remotely close to the level of Bahamut Lagoon), yet I still enjoy it for totally different reasons, like really awesome multiplayer, all the different co-op tricks that can be pulled off (synchronized ground pounds, using players as jump springs, etc.), classic nostalgic Mario gameplay, and memories of playing that game with friends and family (especially all the ridiculous deaths and mess-ups in co-op).

And in rare cases, there are games that are just either insanely glitchy and unfair or plain awful (like Van TT or Quad Desery Fury). Yet I enjoy those games because I don't immediately dismiss them for their questionable quality. Though the game's quality is bad, there are usually some things I find amusing about those games that make me keep playing them (like Van TT's death scenes, the track's "shortcuts", Quad Desery Fury's wipeout animation, etc).