Putting aside a preference for one of the big two over the other (I'm a DC fan, especiallyVertigo and Batman, but also enjoy Marvel, especially Spiderman and X-Men): I actually think that DC and Marvel are both more or less on par with regards to the quality of their villains, on both the silly and the serious extremes.
DC's rogues gallery may include the likes of the Penny Pincher, Crazy Quilt, Killer Moth, The Condiment King, Maxie Zeus, Mister Mxyzptlk, Granny Goodness, the Turtle Man, The Toy Maker, Egg Fu, and multiple gorillas--but it also includes the ah Guhls and their League of Assassins, Vandal Savage, Black Adam, T.O. Morrow, Sivana, Deathstroke, Two-Face, the Reverse Flash, Darksied, Despero, Mogo, Anton Arcane, Lex Luthor, General Zod, Bane, The Court of Owls, Hugo Strange, Sinestro, the Man-Hunters, the Anti-Monitor, Krona, and Earth-3's Crime Syndicate. (Incidentally, I consider The Joker and Scarecrow to be fantastic villains--but that's a whole other post on a rather subjective subject. Go beyond the surface level of the character's appearance and consider stories like Death and the Family, The Killing Joke, The Man Who Laughs, Gone Sane, and Terror. The Joker may be a clown, but he represents the horrors of a truly chaotic, insane psychopath--and quite honestly Marvel's Cletus Kasady was a rather late-to-the-game imitation with the clown motif replaced by a blood red symbiote. The Scarecrow might wear a silly costume, but he and his fear inducing gas meant to represent facing and overcome one's greatest fears.)
Similarly, Marvel''s rouges gallery may include the likes of The Big Wheel, The Rhino, The Walrus, The Mole-Men, Arcade, and the Hypo-Hustler--but it also includes Magneto, Hydra, The Red Skull, The Green Goblin, Carnage, Thanos, Apocalypse, The Sentinels, Loki, Ultron, and Doctor Doom.
I would also extend that same on par in terms of silliness and seriousness sentiment to DC's and Marvel's roster of heroes.
As for DC being outdated compared to Marvel, I totally agree--during The Silver Age of Comics, when Marvel brought back and revolutionized superhero comics. However, by the eighties DC overtook Marvel in terms of writing--especially with respect to the titles written by the likes of Moore, Gaiman, Delano, Grell, and Morrison. Conversely, Marvel and Image put a greater emphasis on the art, especially during the nineties. Today, I would still give the edge to DC but they're closer to being on par than ever. Granted, this is all just my own personal subjective opinion.