Wasn't Starcraft just Warcraft in space?

Wasn't Half-Life just Quake with an actual storyline?

Wasn't TQ just Diablo II set in ancient Greece?

Wasn't C&C just Dune 2 not set on Arrakis?

Wasn't Bioshock just SS2 underwater?

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The point is, good games naturally spawn other similar games. Some of these are better than the original, some of them aren't - time will tell.