1. I'm sure half of the people who have said they mastered certain games might have lied.
2. Mastered for me means "I never have to pick it up again unless for Nostalgia's sake". But do I really need to "MASTER" Gex or Mortal Kombat 4? I mean, Final Fantasy games, granted you need to collect everything and perfect all. But a platformer or a mediocre fighting game?
Well, I tried to follow their definition as close as possible. Most of those people don't even seem to play the games that they claim to have on their lists.
For me, Mastered means I have done everything possible in the game and that I am able to pick it up and do it all over again off the top of my head.
I won't judge your list, however, have you gotten to all of the bonus levels in Gex? Have you done all of the moves (fatalities included) and beat the game with all characters in MK4? If I were not able to say yes to these, I wouldn't put it under mastered. There are quite a few games where I have gotten 100%, but I wouldn't call it mastered.
Not sure just what I'll play next.
Wait a week and a few and you can play GTAIV