I have about a dozen different sets, running the ladder from El Cheapo to an Ultimate Ears custom molded set, which all see use in various scenarios, not just in my GS2.
What I think works best depends for me on the situation, which is why I have a variety. Probably bang for the buck, I like the Etymotic mc5 as the best value. They're not El Cheapo, but they're not custom plugs with three speakers with crossovers either.
You should try out as many as you can for a while. What we like may not be what you like. Good luck!