The Rip-offs, successful, and not so successful.

"List of Marvel Rip-Offs of DC Characters/Teams (That I know of at least):

Anti-Man = Superman, Superman Prime and Prometheus
Blue Marvel = Superman
Blur = Flash
Captain Universe = Dial H for Hero (Alleged Claim, Unable to Confirm)
Captain Ultra = Superman
Clark (An Obscure Daily Bugle Reporter) = Clark Kent
Doctor Spectrum = Green Lantern
Ethan Edwards (A Super-Skrull that was sent to Earth in a rocket as a baby by his parents when Galactus consumed Skrullos) = Superman
Fred (A 1930's styled Mobster from The Microverse) = Fred Flinstone (He's technically DC right?)
Freedom Ring = Green Lantern
Gladiator (Kallark) = Superman
Godkiller Super-Skrull = Granny Goodness and Wonder Woman
Hyperion (Earth-616, Earth-712, Earth-5764, Earth-31916, The Microverse) = Superman
Hyperion (Earth-1121) = Kingdom Come Superman
Hyperion (Earth-4023) = Joe Shuster's original concept for Superman (a bald supervillain)
Ikaris = Superman
Law Enforcement Squad = Justice Society of America
Lois (An Obscure Daily Bugle Reporter) = Lois Lane
Makkari = Flash
Nighthawk (Earth-616, Earth-712, Earth-31916) = Batman
Nova = Green Lantern
Nova Corps = Green Lantern Corps
Owlman (Ultimate Adventures) = Batman
Power Princess = Wonder Woman
Scout (Sentry's Sidekick) = Superboy
Sentry = Superman
Shi'ar Imperial Guard = Legion of Super-Heroes
Speed Demon = Flash
Squadron Supreme = Justice League of America
Thanos = Darkseid
Thundra = Wonder Woman
Vulcan = Superman Prime
Vulcan's New Imperial Guardsmen (Strontian, Pn'Zo, Hodinn, Uncreated, ZZZXX) = Lethal Legion
Watchdog = Krypto
Whizzer (Robert Frank) = Flash (Jay Garrick)
Whizzer (Stanley Stewart) = Flash (Barry Allen)
Woody (Ultimate Adventures) = Robin
Quasar = Green Lantern (Don't you tell me otherwise, it's the TRUTH!)"