Being as I'm in Portland, both Damian Lillard and CJ McCollum come to mind. Both were very successful at small schools and ended up being lottery picks. Both stayed in school 4 years (though Lillard left with a year of eligibility remaining due to redshirting with an injury, and McCollum might have been able to get another year for the same reason), but I've never heard either say they would have transferred to a bigger school if they didn't have to sit a year. But they are also just two examples, and I'd say by far they were exceptions, among the hundreds playing D-1 every year.
I know we see lots of graduate transfers nowadays, but how many of them are really impact players? Admittedly I don't follow CBB like I used to, but the ones I have heard of haven't been much more than rotational players who just want a change of scenery for their one final year and don't really make a big difference.