National Championships won since 1970 (includes shared)
5-Nebraska, Miami
4-Oklahoma, USC
3-Notre Dame, Alabama, Florida
2-Florida State, Penn State, LSU
1-Pitt, Georgia, Clemson, BYU, Colorado, Georgia Tech, Washington, Michigan, Tennessee, Ohio State, Texas
I'd say, since you ask about when we've been dominant, those numbers speak for themselves. As husker98 stated we have no more heartbreak than the next team. As a matter of fact, we have the most wins, highest winning percentage, and most National Championships since 1970.
If that doesn't show we've not been frustrated but rather lucky as fans, than I don't know what to tell you.