Lelando Wrote: Arma 3 is a pretty good sandbox game. I'd check into it if you love creating your own experience from nothing.
The Arma series are sick games, from basic TDM to Patrol Ops and City Life mods. I love RP games but I've been stuck on SAMP for the past 10 years. It's died down a lot recently but I'll be making the jump to GTA5 RP when I get a new PC build. I suppose it's down to preference, I liked GMod for it's sandbox ability but I don't think I've found anything quite like it - apart from Minecraft which got boring 8 years ago.