I second Saga of the Seven Suns by Kevin Anderson. An excellent read and just the right length for my tastes. Also, in no particular order of preference:
The Night's Dawn trilogy by Peter F. Hamilton
Pandora's Star by Peter F. Hamilton
Judas Unchained by Peter F. Hamilton
The GAP sequence by Stephen Donaldson
The Culture sequence by Iain M. Banks
The Xeelee sequence by Stephen Baxter
The Mote in God's Eye by Nicen & Pournelle
The Forge of God + The Anvil of Stars by Greg Bear
The Eon sequence (Legacy, Eon, Eternity) by Greg Bear
A Fire Upon the Deep and A Deepness in the Sky (separate stories) by Vernor Vinge
Hyperion and Fall of Hyperion by Dan Simmons
The Uplift War trilogy (Sundiver, Startide Rising, Uplift War) by David Brin
Those are the ones which immediately spring to mind. Whether they're all proper "Space Operas" I'm not entirely sure, but they're certainly some of the very best SciFi books I've read.
Last edited by Belfaborac; 01-22-2011 at 06:35 PM.