>>121572386Gold Key is worth looking at for Russ Manning's art
Valiant (when Shooter was overseeing) had a pretty good story going, after Shooter leaves the quality varied wildly. I think supposedly it counts the Gold Key run as part of its continuity (they just take place before Magnus #0), but I haven't been able to confirm that.
Acclaim reboot had Tom Peyer doing a drastically different Magnus which is still worth reading through even if it's nothing like the Gold Key/Valiant Magnus.
Dark Horse one was decent.
I didn't get around to reading any of the Dynamite stuff.