Unlike the Spiders, the Rams have somewhat of an argument, though it's still pretty weak.
They finished the season at 27-6 and 13-5 within the Mountain West Conference -- but that's one of their problems. Even with a team like San Diego State in the Mountain West, the Rams strength of schedule suffered. They finished the season with the 110th-best schedule in the nation -- that's just not good enough.
On the other hand, the numbers suggest that Colorado State is still one of the best 68 teams in the nation. The Rams are 57th in BPI and 60th in nERD, and are the 28th most efficient offense in the country. Colorado State might have been good enough to make the field, but their strength of schedule seems like it weighed them down, and ultimately kept them out of the big dance.