Marvel's strength scales go up to around 100 tons for their most powerful characters
Another thing to keep in mind with that figure is that for a while now 100 tons is basically the 'we stopped caring about numbers now' point. Hulk, Thor, Hercules, the Abomination, etc., have been shown lifting more than that. And even for weaker characters they get shown to lift more than whatever class they get put in because the ton classes were derived based on a military press or some specific method of lifting that used a very isolated muscle group and didn't entirely reflect what characters could do. And of course, that authors have come and gone since who favoured theatricality - or filthy lucre - over established limits.
Most notably... time travel. If Lex has managed this as well, I'll relent that point... but I don't recall offhand him ever having done so.
Wikipedia says several pre-Crisis stories depict him as having mastered it.
I think Luthor would probably be smarter, just because DC does everything on a grander scale. It's like the strength measurements, except there's no easily quantifiable unit for intelligence. But if there were, DC would tack on more zeroes at the end of whatever figures they came up with for their characters. And I think there's a lot to be said for Lex Luthor being a Superman villain: with his intelligence alone Luthor consistently challenges an alien being regularly criticized for being nigh-omnipotent and an extended family of beings of like power.
Not to short change Doom: he's done a lot of rather impressive things. Time travel, coming from a Marvel character, really fails to inspire awe in me. Maybe it's just that I'm disproportionately aware of it in the Marvel universe, but it seems like a lot of Marvel characters are able to time travel. When he stole the power cosmic from the Silver Surfer, that was a lot more impressive to me than anything he could do with time travel.
The thing I would think that gives Doom an edge over Luthor is that Luthor way more obsessed with Superman. During that whole 52 thing where Superman had no powers and lived exclusively as Clark Kent, Luthor basically spent the entire time obsessing about Superman, enacting one evil scheme whose ultimate purpose was to lure out Superman, and getting angry at everyone because they did not believe some new superhero was really Superman in a new identity that Superman adopted solely to troll Lex Luthor. Doom, meanwhile, is globe-trotting, finding time to be part of Norman Osborne's Cabal, making booty calls to Morgan Le Fay, collecting My Little Ponies, jobbing to Squirrel Girl in full glorious not a Doombot canon, running Latveria, failing to destroy Reed Richards, giving third person speeches, and all of that. Luthor's not going to do his best work unless he's got the carrot of destroying Superman dangling in front of him, but Doom'll go and do something supervillainous for whoever - the Fantastic Four, the X-Men, the Avengers, the Great Lakes Avengers, the Defenders. Doom doesn't care.