The one thing WoW has done really poorly is rewards at level 60. Restricting epics to raids was a mistake in my opinion. For most of the game there was a decent balance between rewards for instances, and rewards for quests. However, at 60, the balance swings way too much towards instances. There are some questlines that are epic in scope, and really deserve epic rewards.
Here's my list of quests that deserved epic rewards:
1. Tirion Fordring questline
This is one of the best loved questlines in the game. It takes you across Eastern Plaguelands, to Stratholme, and to Hearthglen as you help Tirion Fordring seek redemption. It's a gorgeous questline, and the rewards are quite good, but if they were bumped up a notch, this quest would be perfect.
2. The Lich, Raj Frostwhisper questline
This quest takes you from Scholomance, to Stratholme, and back to Scholomance as you seek the key to defeating Raj Frostwhisper. It's quite long and involved, and very few people actually do the whole questline. I've actually gotten more whispers about my Warblade of Caer Darrow than any other piece of gear. By the time most people would have completed the questline, they've moved on to raiding instead.
3. Hero of the Fallen Horde questline
This one has you fighting in the Blasted Lands, seeking to destroy Razelikh the Defiler. I remember forging the Sword needed to defeat his Servants, and the questline culminates in an awesome battle atop the Defiler's Rise.
4. Dawn's Gambit questline
I'll be honest, I haven't even finished this questline yet. It's the one where you have to collect the eggs from Upper Blackrock Spire and then go to Scholomance and defeat Vectus and his students. I just don't feel like going back to UBRS.
Personally, I love these long, involved questlines. They are a fair amount of work, and really deserve to have better rewards. Hopefully, end level questlines in Burning Crusade will have improved rewards.