I need to get to more of my backlog (Parasite Eve Valkyrie Profile 1 and 2, and my Fan Translated Front Mission 5). I did hammer the hell out of Diablo 2 and 3, but I had to move on and make time for new games.Before i watch your video , i tought what games can be mentioned and first thing comes on my mind were Chrono Trigger/Cross lol.
Yes, you need to play Chrono Cross at least 3 times to unlock all characters, because you cant get that Rock Star guy, and Gleen in same walktrough, and i think there is one more ,but i forget which lol.
Some other games in top if my mind:
Parasite Eve PSX: once you finish game, optional tower opens, Crysler building, with 77 HUUUGE random generated floors, bosses each 10 floors and you can save only at beginning at floor after you finish previus boss, so there was a lot of retrys, passing 10 levels, facing boss, die by him, retray all past 10 leveles, with levels randomly generated again, and you need to explore them all again to find all secrets weapons and armours etc . Very chalenging, but very fun and great replay value, and you get alternate game ending as well.
Valkyre Profile 2 ,PS2: altough when you start new game plus, you basicly start from scratch again, you do , similary to PE, get another huge tower to complete in this game after you finish game once, and it is loaded with lots of strong bosses and secret characters.
Front Mission 5 : this one have 2 extra modes to choose after you finish game once, easy mod ,in which you keep all that you collected in game,and hard mode, in which you keep nothing, enemies are harder, BUT , survival simulator opens another 50 levels (only 50 in first game playtrough) in which it is possible to get best game equipment (not possible to get even half of great equipment in first playtrough or easy mod), but it requures a lot of try and lot of playtroughs, and 90 of those levels are randomly generated, so it dont get bored very, easy, high replay value. Also, nothing stops you to first finish game once, then play it in hard, collect all best equipment,and then start third playtrough in easy level, to keep all equipment.
And ,not worth mentioning all Diablo/TitanQuest/Baldurs Gate games i guess, in which new game plus on higer dificulty is not option, but requrment lol.