Left 4 Dead 2 was censored in Australia, until the classification board started allowing R-ratings for games. It was re-released (if I remember correctly) without the censorship.
You are correct, swastikas (and other symbols of the national socialists) had to be replaced/removed in Germany in the past. Nowadays games have been recognized as art form and a game developer can request admission to the German market without removing the symbols first. I'm not sure if there's already a game which did this on the market.
First game that was allowed to do so was “Through the Darkest of Times”[1] by Paintbucket Games.
I’m not sure Wolfenstein or l4d would get a clearance though.
Would be an interesting case. After all, 'Inglourious Basterds' was allowed to show them and it seems hard to argue how that movie is different from a Wolfenstein game.
Recent Wolfenstein games are all about a timeline in which the Nazis won WW2 using advanced technology looted from an ancient superadvanced civilization.
So I could see "an entire world where the Nazis won WW2, and the resulting propaganda everywhere" getting a hard look.
Yes, games still do (all Wolfenstein versions were either illegal or censored). Not merely the Swastika used in Nazi Germany; also other symbols from Nazi Germany. See this video comparison for examples [1]. Summary: at least Swastika, SS bolts/runes, and Iron Cross (even though that one was used in Germany way before Nazi Germany). In this video they're using mostly the Wolfenstein logo as replacement but there might be some easter eggs as well.
IIRC in the past blood was also made green but perhaps I'm confusing with other countries.
L4D was also censored in Australia I think.