First, a surprising benefit of this thread are the mentions and discussions of games I was unaware of. The great thing about ENworld is the diversity of people with diverse gaming experiences who are members. What I don't like about ENworld is that it is mostly a D&D discussion board and trying to start a discussion about any other game just gets buried in "TTRPG Other". I with there could be more system specific forums. When I'm running a non-D&D game I generally go to other forums and Reddit to discuss. I wish the forum list would be more representative of the diversity of coverage in ENworld's news posts. ENworld discusses lots of games in various news posts, in their flagship podcast, and they even have a Not D&D podcast, but the discussion forums don't reflect this at all.
Yeah, this is a big one for me as well. I would happily play in a Star Wars, Star Trek, Expanse, Lord of the Rings, etc. game and I wouldn't care if the GM does violence to the canon. But I wouldn't run games in them, because many/most players want to play these games because they enjoy those worlds and expect some level of staying true to canon.
I ran a one-shot of The Expanse and I felt even more constrained by the canon because it is much more narrow lore. With Star Wars or Star Trek, you can at least just make up some world and new aliens and play outside the politics and events covered in the movies, TV shows, and books. The other problem I had with The Expanse is the hard science element of it. It really only came up in space travel and, to some extent in fights, and just made me want to handwave most space travel and I found fighting in a space ship or on ground more fun than spaceship on spaceship fighting.
At the same time, a game like Starfinder doesn't scratch my sci fi itch. To me it just plays like D&D with lasers. I would love to find a system more grounded in science (with some highly speculative, sci-fi elements like FTL travel or wormholes), but abstracted so you don't have take a correspondence course in physics to play it "correctly." Also, one not weighed down with decades of TV, movies, and books.
I should take a closer look at Traveller, but when I read discussions about it, it feels like it might be more crunchy than what I'm looking for. If I had the free time, I'd like to kitbash something with Cortex prime, but I just don't have the time to do everything from scratch.
I love Paranoia, but prefer to run one-shots or mini-campaigns. You also need players who can enjoy the silliness without going overboard and becoming so obstructionist that the story can't move forward.
For "silly" games, my favorite remains InSPECTREs. It is such a great small-group beer-and-pretzles party game and I always have a blast. But it works best with more outgoing players as it is very improvisational. I could see more introverted and passive players finding it stressful and feel like they are being "put on the spot."
Horror and suspense are hard to pull of in most games. Dread helps with the jenga tower mechanics, but that also makes success dependent in part on dexterity of the players. I also like Grim. One page of rules and a deck of cards. Call of Cthulu, Old Gods of Appalacia, The Magnus Archives, and games like that would be fun to play in with the right GM, but I would have trouble running them and capturing much of any of the feel of those stories.
I'm really enjoying running The Enemy Within for Warhammer Fantasy Roleplay 4e. It is a nice mix of D&D inspired fantasy, Call of Cthulu inspired cults and dark powers, lots of political intrique, less overt magic, more renaissance tech, dark and grim but with an 80s punk sensibility of not taking itself too seriously. I'd much rather run a long campaign where you can dip into horror, suspense, combat, political intrigue, romance, etc. without the entire premise of the campaign being based on one genre.