I know about GOG.
But, i am looking for newer games. One of my worries is, what happens if a uninstall a game. Do i have to pay for it again? Or can i just go to the site and download without paying again?
Most services work like Steam, i.e. the games you own are tied to your account. So if you log in with your personal data then you can usually download, install and uninstall any of your games as often as you like. If it would be any different then I don't think that the company offering the "service" would still be in business
.
If I were you I'd worry more about the um... "patchability" of downloaded games. Often times you can't just install the retail patch but need to wait for a special version of the patch to be released by the dev or the service provider. These patches are sometimes severely delayed compared to the retail patches which can be a real PITA depending on how much you like a game and in how dire need of a patch the game is.
Same goes for (free) DLC/add-ons/updates/expansions sometimes. You will always need to pay attention that what you are downloading or buying from any place
other than your provider's site is compatible with
your version of the game.
And not sure if you care about mods but once more the same also goes for mods. A lot of mods do work with downloaded games but sometimes the mods will only work with the retail version of a game.
Regarding all of the above, I have no idea which service is the most patch-/update-/mod-friendly one. Maybe someone else can provide the answer to that.
Personally (being from Germany) I only use GOG on a (more or less) regular basis. Steam sucks for someone like me who prefers original, uncut English versions. Steam has built-in IP detection so if you log into Steam from Germany you mostly get German-only, censored and overpriced games.
Only other services I have used is EA's downloader for some Battlefield booster pack(s), SOE's (Sony's) service for some Star Wars Galaxies expanions and Blizzard's store for digital downloads of Diablo 2. All of those worked like a charm.