For older games I'd argue GOG is the better bet, hell in general GOG is the better bet because it's DRM free, but more importantly for low IQ unable to troubleshoot Philip: They usually make sure the game runs fine right out of the box which Steam couldn't give less of a shit about.
Now sure, Doom 2 runs fine on steam if you're not a braindead ape, but that's the thing, he is a braindead ape. He should be making it easier on himself. I mean honestly buying Doom 2 at all is exceptional because it's freeware and ZDaemon or GZDoom (because online co-op doom is rad) run it better than dosbox could ever hope to.