I know you said leveling up system, but there are also games that as they If you' re interested, some games like that are GTA IV, Red Faction: I'm starting to get sick of games with level up system and griding. Kongregate free online game Level Up! - Sandbox Platform RPG ComedyRun, jump, collect gems and talk to zany NPC's to level up!. Only games I found through Google was Ultima Online and/or sort of like Skyrim's skills, like if you craft something; crafting level goes up.
Games like level up Video
Games like level up - ein wenig