These are my picks for best comic book covers of 2008 - - all covers that made me want to buy the comic to read the story inside. Links are to reviews of the issues and the artists' sites:
Action Comics #872 cover by Gary Frank
Birds of Prey #125 cover by Frank Quitely
100 Bullets #98 cover by Dave Johnson
Army@Love: The Art of War #5 cover by Rick Veitch
Young Liars #10 cover by David Lapham
Ms. Marvel Special: Storyteller cover by Giuseppe Camuncoli
Secret Invasion: Front Line #4 cover by Juan Doe
Tiny Titans #7 cover by Art Baltazar
Madame Xanadu #3 cover by Amy Reeder Hadley
Justice League Unlimited #42 cover by Christopher Jones & Mark Propst
And my favorite of the year, the irresistible Ghost Rider versus murderous nurses:
Ghost Rider #21 cover by Marko Djurdjevic
Relatedly, here's Robot 6's 25 Best Comic Book Covers of 2008. There's no overlap at all between Kevin Melrose's list and mine.
*Buy "52: The Covers" at Amazon.