The game looks as legitimate as anything in CUSA.
NDSU has a little 19,000 seat dome and it's sold out and loud.
Can't say the players look any smaller, slower, or less athletic than their counterparts at the bottom of FBS.
The fans look significantly more involved and excited than fans at most CUSA games.
NDSU runs an interesting offense, and they use a real snap count, not the "clap ya hands" thing.
I looked up their revenue and it's essentially the same as ours.
What if they got a big head and went FBS? It wouldn't work. I doubt the MAC would have them; they're 3 states away from the closest MAC school. They'd end up cobbling a coast-to-coast schedule together like NMSU has to. Their fans wouldn't know about most of their opponents.
All of this is to say, most schools at that revenue level would be better served by staying FCS if they have a decent FCS history. CUSA's own Old Dominion is the example that pops to mind.
Another implication is that the dreaded "Mid Major national championship" tournament would probably generate more excitement than the G5 bowl season does. I've never been a proponent of that (preferring to call for other changes to the status quo), but it's hard to ignore the obvious when it's right in your face.