The top 5 exclusives for the ps3 that will sell are the following:
5) Little Big Planet
4) Socom Confrontation
3) Final Fantasy XIII and Final Fantasy Versus XIII
2) Resistance 2 ( amazing multiplayer mode (60 players online!)
1) God Of War III
What do you mean by "Top Seller"?
If it is 1 Million units sold, I think that is a safe bet for all games (except Little Big Planet) ... If it is dramatically higher than that (say 2 or 3 million units) most of the games will fall short.