I'm going to assume you're referring to JRPGs, since I can't think of a single western RPG that was turnbased. In that case, let's take a look at the top-selling JRPGs of this generation:
1. Pokemon Diamond/Pearl (turn-based)
2. Pokemon Mystery Dungeon: Explorers of Time (I assume it's turn-based)
3. Pokemon Mystery Dungeon: Blue Rescue Team (I assume this is turn-based as well).
4. Monster Hunter Freedom Portable 2G (don't know if this series is turn based).
5. Pokemon Ranger (I'm not sure what this game is even about, but I'll guess turn-based).
And if we're not counting Pokemon, then the list looks like this:
1. Monster Hunter Freedom Portable 2G (again, not sure if this is turn based).
2. Final Fantasy III (turn-based)
3. Crisis Core (turn-based)
4. Dragon Quest Monsters: Joker (I'm pretty sure this game is turn based).
5. Mario & Luigi (I'm guessing this isn't turn based).
I'd love corrections, but it seems that turn based RPGs are still fairly popular.
