Um...Hello, it's Late anyone? I cannot believe that hasn't been mentioned.
To me, the term 'epic' means something of a grand scale, or a big sound. A perfect example to me of an epic song would be something like GNR's 'November Rain' or Bon Jovi's 'Dry Country.' Not too many of STP tunes are lengthy in that sense. (Except Where the River Goes, which to me isn't really epic, but more of a jam) If I had to pick a few epic tunes, I guess I would go with the following.
Kitchenware and Candybars
Adhesive
Glide
Atlanta
Hello, It's Late
These songs give me goosebumps more then anything. Sometimes, I'll just lay in bed and stare off and loose myself in the music.