That, but the GM matters too - and if they're lucky enough to have them, any co-GMs or other assistants. Everyone at the table and the game you're playing contribute to making the stew taste right - or wrong.
You might also consider the space you're all gaming in. You often get a different experience from playing at home, or a con, or at a game store, or in a public venue that isn't game-connected, even when the group and game are otherwise identical. To extend the stew metaphor, the pot matters too.