Other. Our group is usually somewhere between 4 + DM and 6 + DM. Sometimes 3, once I think we had seven, and maybe we'll be seven again soon, permanently. Unless a couple of players can't make it.
I have 6 steady players. That's a good number for me. I will play with as few as 4, but I like 5 or 6. I wonder if they went with 5 because its difficult to get new DMs going?
There needs to be a second poll to go along with this one, regarding how many characters are in your game's adventuring party. 5 players does not equal 5 characters, once you factor in party NPCs, players running multiple PCs at a time, and so on.
While the game design seems to assume 1 player = 1 character (thus making a standard party of 4 in 3e and 5 in 4e), is this assumption correct? I suggest that more often than not, it isn't...
6 players. I don't think I've played many times with less. I've certainly never played in a game with only 4 players. So much for the 3.5e system. It was always more fun to have more players.