"Play like you're five" is excellent advice, I think. Sometimes people get too fixated on the goals in the game and forget the rest of the opportunities... that, I think, is at the core of a lot of complaints about games being too short.
I'm not a "fast" player. I don't sprint from objective to objective. I may never, ever do a speedrun in my life, but there's nothing quite like getting "into" a game by going outside it. I mean, it's amazing to get up on an odd ledge somewhere and just gawk at the scenery from an odd angle; climbing the Agency Tower in Crackdown and looking down at the city, or to the top of Cairo Station in Halo 2 to get a clear view of the Earth, or to the SatCom arrays in Fallout 3 to watch the MIRVs rain down. "Tricking" and map exploration add a lot of fun to the game.
(One notable "odd" achievement had a player take the Gold Elite you encounter at the start of the Halo level "Assault on the Control Room" and kite him all the way to the end of the level, the successful run taking something like an hour... just because. Another, famous one was the "Warthog Jump" video wherein a player used grenades to "punt" a Warthog jeep over an arch.)
If there's one thing to admire about Achievements, it's that often they're used to prompt players to try this sort of off-the-wall play.
-- Steve
