TF2 is the biggest free FPS out there, and one of the biggest FPSs out there in general. So when a game comes out that is:
*strictly multiplayer only
*has cartoon style graphics
*has game modes that involve capturing points and moving payloads
*and has unique and easily distinguishable characters with their own strengths, weaknesses, and set of skills,
comparisons are gonna be inevitable because these are all characteristics that TF2 has.