Many years ago when my gaming spirit was youthful I have completed almost each game I have played on 100%
Most of them on PSOne, some on Nintendo 64, few on PC.
Best and hardest I remember: Final Fantasy I, II, VII, VIII, IX, Vagrant Story, Tenchu I, II, RoninBlade, Metal Gear, Gran Tourismo, Pro Evolution Soccer
Mario 64, Batman - Arkham Assylum, some LOTRs and some Age of Empires and many more.
I always choose well the game I am going to play so there is no chance it will make me bored.
Only game I have just jumped in is RS

If I havent completed a game on 100% is dint even considered it for beaten.