If by 'rivalry' you mean CU is a team I daily pray to God to destroy as the heathen of Sodom, then yes, you have your rivalry. But if 'rivalry' means a generally good-willed generational matchup between two equally worthy opponents, I ROFL at you, sir. When it comes to the Big XII North I generally root for the teams from our conference to beat the south and their non-con opponents. When KSU shanks Texas two years running, I laugh at Mack Brown. When Mizzery routes Illinois, it's fun to watch. But when Colorado plays any team, and I don't care if it's the Miami Thug-U Hurricaines, I pray for CU's utter embarrassment. To me they're Baylor North, half-retarded adopted brother of NU, at best to be treated with a kind of mild neglect. If they went 0-12 every year it it would still not be satisfactory. Classless, classless fans. I'll never forget the game where an entire section of their stadium had to be removed for throwing things on the field.
Good luck with your Colorado State rivalry.