At the start of the song, the sound you've got for the instruments is okay, because they're all getting exposure. Once the electric rhythm guitar comes in, though, problems arise.
The piano playing the main melody is barely managing to voice itself with the rhythm guitars. But, actually, the piano problem isn't as big once the lead guitar comes in. You can barely hear the lead guitar, right? You want everything important (especially leads!) to be legible, so raise the volume on things to even them out. The rhythm guitar, piano and lead guitar all fight for pretty much the same space in the mix, so to have them work together, you've got to EQ and pan them appropriately.
The choir works out all right as a pad, so it's good as it is.
The drums are generally well mixed, but I think you could spare the cymbals some lower frequencies as well. Compared to the snare and kick, they don't hold the same.. power? Though, sometimes, like at 1:38, the kick is too strong for how the rest of the instruments sound.
Also, there's a lack of bass throughout. It's okay for the softer sections to be missing it, but it's definitely needed during the "upper" parts of the song. It could be covered by a bass guitar or maybe deep strings or something. It'll help the overall mix a lot.
The acoustic guitar always sounds good as far as I can tell.
I really like the drop at 2:43, though. It sounds very "epic," even when it's using the same progression. The solo seems like it'd be pretty hot, as well.
Just keep comparing your mix to a song with the sound you want. Keep changing volumes, EQing and panning until everything feels just right. ^^