I don't think Command and Conquer, Warcraft 1&2, Star Control 2, Ultima 6-8, Wing Commander, and/or X-wing and Tie Fighter came out for SNES
Ultima 8 was AFAIK DOS-only. There was a SNES version of Ultima 7, but it was largely considered a joke. For one thing, Nintendo couldn't stomach the plot, which was about investigating a series of rather gruesome murders, which somehow mutated into 'kidnappings' in the SNES version.
The original game was about 20MB all told, pushing the limits of what was technically feasible on the PC at the time (it used "unreal mode" which allowed the 16-bit game engine to access a 32-bit address space, but couldn't work under Windows or EMM386). As a result it was chopped down significantly, losing the ability to recruit party members or even select the player's sex.
AFAIK they never even attempted to port Serpent Isle, aka Ultima 7 part 2. Given the apocalyptic ending I can't say I'm surprised.
Although Doom without multi-player is kind of pointless.
Depends. If you've got a hundred odd add-on levels for it it's got a lot of staying power. 'Course the console versions didn't have that either.