Fortunately I avoid anything -core like the plague. Synths are great but some people just can't handle music that happy sounding I guess. It's cheesy as hell, but I love stuff like The Final Countdown and Rainbow in the Dark or anything by Rhapsody. I also love classical music though and a lot of the power metal synth playing is just ripped straight from Vivaldi/Bach/Beethoven which is never a bad thing in my book.
How can you listen to something like this and not feel good?
http://www.youtube.com/watch?v=W8Gqd0XPKsI