I would’ve made the same decision that you made simply because LA is a great place to be. I’m not too familiar with game design, but for overall CS I’d say, Michigan > UCLA > Purdue > RPI.
With regards to UCLA CS being “mediocre”, it really depends on what your definition of “mediocre” is. If by “mediocre” you mean in comparison to all the universities in the U.S., then UCLA is far from mediocre. If you’re comparing UCLA to other top schools, then you could probably call the CS department “mediocre” in the sense that it’s not what UCLA is really known for and it’s not the first thing people would think of when they think of top schools for CS.
From my experience growing up in the Bay and interning at SV tech companies, the hierarchy for undergrad (alphabetically listed) would probably go something like this:
Tier 1:
Berkeley, CMU, MIT, Stanford
Tier 2:
Cornell, Illinois, Harvard, Michigan, Princeton
Tier 3:
Georgia Tech, Texas, UWashington, and other well-known CS schools like Wisconsin. UCLA would belong in this tier depending on regional bias.
All are very good schools and will provide you with tons of opportunities to succeed.