Ok, here is a gaming observation that I'd like to put into text, that people who are much more clever than I have already arrived at, and talked about, but I'm going to give it a stab here myself.
If you and I and some other folks are going to sit down at a table and play a Role Playing Game, we need some idea of what we're going to play. Now, I'm not exactly talking about *which game we're going to play*. I'm talking about what we're going to play. But this can work in two ways. I assume that 99.9% of the time when people sit down to play, they already know which game they're going to play. Let's assume its D&D. So we have that, but do we know what we're going to be doing? No way. That has to be refined. We either need to let the DM say "This is what we're doing", and we all go along with it, or we need to have a discussion about "This is what we'd like to be doing", and figure out where to take it.
"I'd like to play a game about mystery and exploration, and discovery of ancient evil, and possibly going bat-shit." Call of Cthulhu, check.
"I'd like to explore dungeons, kill gobs and gobs of monsters, get XP, and get levels. Oh and magic swords." Dungeons & Dragons, check.
"I'd like tons of intrigue and mystery and character development and double-crosses and fancy parties." Vampire, check.
That was a fun exercise. Anyway. Even if we all sit down at the table and say "We're playing D&D", or "We're playing Vampire", there should be a discussion about what we're going to be doing. Because its super safe to say that not every D&D game, or not every Vampire game is the same. Maybe we want to do a Thieves Guild game in D&D, or we want to play a brutal combat game of Vampire instead of political intrigue.
'Cause both the players and the GM should be getting something that they want out of the experience.