I Think a few candidates are as follws...
Red Hot Chili Peppers
Kings of Leon
The Flaming Lips
Monsters of Folk
In no order, blink 182, the all american rejects, coldplay, radiohead, simple plan, fall out boy, linkin' park, jet, good charlotte, arctic monkeys, all time low, green day, the spill canvas, plain white ts, boys like girls, bluejuice, british india, weezer, counting crows, creed, cobra starship, escape the fate, death cab for cutie, the getaway plan, escape the fate, the friday night boys, gym class heroes, grinspoon, infected mushroom, kiss chasy, jimmy eats world, the living end, nickelback, my chemical romance, panic! at the disco, the offspring, reed hot chilli peppers, the script, something for kate, thirsty merc, thursday, the sundance kids, yellowcard, we the kings, wolfmother, white rabbits, 3OH!3.
RHCP aren't as good as they use to. Escape The Fate is an awesome band with Ronnie, but there new stuff blows! Metallica released one crappy album(St.Anger) and one okay album(Death Magnetic), so they wouldn't be on the list. Megadeth released 1 bad album(Risk), okay albums(The Syatem Has Failed and United Abominations), and one excelent album(Endgame).
So I would say Megadeth.
I'm really into this band called Sound of Guns right now. They're an awesome new band from Liverpool. They kinda sound a mix between Foo Fighters, Led Zeppelin, The Walkmen and The Doors. Apparently Zane Lowe has been raving about them too. Check out their myspace guys!