In no particular order:

• Sword Art Online S1 - It’s hard to beat the terrific setup, the stakes, and conclusion for the Clannad arc.
• Shangri-La Frontier - The writer really captured gamers’ mentality, and we even see the developers, yet the game itself still retains an air of mystery like a player experiences initially.
• Villainess Level 99 - Someone else who abused RPG mechanics, but a charming goofball for laughs.
• Solo Leveling - Power fantasy with RPG mechanics
• Log Horizon S1 - Competence porn for guilds