erm.....from what i understand epic means heroic, so if we go by that definition:
Led Zeppelin - Battle Of Evermore / Achilles Last Stand
If we take it in the sense that it is music "surpassing the ordinary in scope or in size" then (an odd mix):
Pink Floyd - Comfortably Numb / Echoes / One Of These Days
Opeth - BWP / The Moor
Faith No More - The Real Thing
Metallica - Orion
Mike Oldfield - Tubular Bells
Moody Blues - Nights in White Satin
Nevermore - This Godless Endeavour / Dreaming Neon Black
Type O Negative - World Coming Down / Wolf Moon / Anesthesia
Black Sabbath - Spiral Architect
Vangelis - Bladerunner
My Dying Bride - Crown Of Sympathy
LTJ Bukem - Music / Demons Theme
The Aphex Twin - Heliopsphan
The Future Sound Of London - Papua New Guinea
Fear Factory - Resurrection