When comparing Garry's Mod vs Cities: Skylines, the Slant community recommends Cities: Skylines for most people. In the question“What are the best singleplayer games on Steam?” Cities: Skylines is ranked 28th while Garry's Mod is ranked 112nd. The most important reason people chose Cities: Skylines is:
At a total of 36sq.km of area to use (compared to SimCity 4), there is a large amount of room to build and play.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro The games mechanics and mods allow for ridiculously funny gameplay
You can do some really crazy things in this game thanks to all of the community mods available as well as the built in, in game tools. Pretty much any scenario can play out in the game, if you so desire. Of course the winning combination of funny tends to be when players are just goofing around.
Pro Tons of community made add-ons allows the game to continually grow
Garry's Mod has a wide variety of community made add-ons, which deeply extends the games content and versatility. Pretty much, if you can think of it, someone has probably already made it.
Pro Large scale
At a total of 36sq.km of area to use (compared to SimCity 4), there is a large amount of room to build and play.
Pro Steady Stream of new content via DLCs
DLCs are optional, they do go one sale. Plus when a new DLC is released a bit of the content is released into the base game.
Pro Depth of field
There is a depth of field effect that will blur distant buildings, which mimics Sim City's diorama effect. It can of course be adjusted with a slider as to how much or little to use.
Pro Large Amount of Workshop Mods & Assets
With almost 150 thousand assets and mods, you can totally change the gameplay and look of the game
Cons
Con It has nothing to tell as a campaign. Tastes like void, that is "meh".
Con Previously free to download
Garry's Mod used to be a free download but it is now a paid game on the Steam store.
Con Tons of bugs
At least in earlier versions.
Con Resource Heavy
If your computer doesn’t have decent specs, don’t expect to be able to run this game smoothly.
Con Expensive
If you want more gameplay features, you have to buy expensive DLC, but you can get them on sale sometimes.
Con Can be difficult to glean what one has done wrong in game
Cities: Skylines has difficulty letting the player know what they have done wrong, which results in a lot of head scratching.