Emulating old games is almost entirely safe. Sure it might be possible for a rom to have something injected in it that takes advantage of some emulator vulnerability but it's extremely unlikely and I've never heard of it. Keep on doing that.

Modern games (or any other .exe files) are very risky. And you may never know you have a keylogger.

If there was no risk I'd pirate modern games. However you usually can't play online anyway. And having all my games in one place on steam is very nice, with cloud saves and family sharing too.