Resident Evil
There is enough characters and monsters to make a fully fleshed out SRPG.
Classes would be based on weapon type. (Pistols, shotguns, bolt action rifles, semi auto rifles, heavy weapon, melee)
Add in extra classes like a "beast tamer" where you can control BOWs (birds, dogs, lickers, hunters, crimson heads, special summons like Mr X or Nemesis)
You would have over 100 bosses to choose from through the series, so every stage could have a boss.
Initiating the algorithm for combating unknown foes...