Quake vs Unreal

Last week, I made the mistake of swapping Unreal with Quake, while defining Quake 4. This isn't the first time I made this mistake, so maybe its time for some investigation.

Both are Sci-fi first person.
Both have had at least one "Tournament" release.
Quake started in 1996, Unreal in 1998. Which all seem like the same these days.
Both had ridiculously large guns, that seemed very similar in many cases.
Both keep having sequels.
Both were strait forward, meaning, little reward for stealth, etc
Both had un-memorable story lines. (okay not fair to Unreal, but true)
Both had similar multiplayer games (CTF, Deathmatch, etc).