When the Marvel Champions Core Set first dropped, we were given five heroes, three villains, and five modular encounter sets, not to mention four aspects. This provided an amazing amount of variety straight out of the core set:

5 Heroes x 4 Aspects = 20 basic hero modes to play
3 Villains x 5 Modular Encounter Sets = 15 villain / encounter match-ups to face
If you took every hero in every aspect through every villain / encounter match-up, you’d have 300 games to play.