Even if this was objectively true, which it isn't (from some perspectives the college game is more competitive, from other perspectives the NBA is more competitive), what exactly is the difference between competition and entertainment for a fan or spectator? What is it that makes competitiveness attractive? The fact that it's entertaining.
Anyway, this whole argument putting the two at odds is kinda silly IMO. A basketball fan can enjoy both and IMO they should. For me the NBA kinda sucked this year because the champ is a foregone conclusion and my favorite NBA team sucked and gave me no joy, but my favorite college teams were surprisingly great. So I watched more college basketball. Four years ago the opposite was true. The NBA is clearly superior basketball, while the college game's format makes it more unpredictable and gives it the more exciting (but far shorter) postseason. They're both awesome.
I've never understood why people feel the need to choose sides on this And the best part is- if you like both there's that many more games to watch and enjoy, which makes it even easier to ignore your family, friends and responsibilities!