You folks are assuming that he only has three cases of games! Clearly, what he showed us is just "the minty collection" -- I bet there are 1-2 more cases with opened, non-minty games for daily use.
Well, he listed 481 games.
Each case can hold, at most 5x35 CDs (single case) = 175 CDs, so 3 cases is 525, and by the time you discount the games that came in double CD cases, I would guess that the number is pretty close to that 481 number.
For the record, George Palamara had a complete PCE collection, and was trying to get new copies of as many PCE games as he could, as a supplement to his "playable" versions.
My collection is of 884 unique PCE/Duo titles -- and 99.7% of them are used. There are a few unopened ones in there -- but that is only because I received unopened ones and sold off the earlier opened ones... I have played every single PCE game that I own.
-bt