Don't be surprised to find more game-worlds within-games like this sooner rather than later. Perhaps the most engaging game-within-ROBLOX I found was Pokemon.

Roblox features a variety of Pokemon games, and they focus on different aspects of gameplay, ensuring there's something for all players.

Like a lot of the upcoming games on this list, Anime Battle Arena puts the focus on many people’s favorite part of anime - the fighting. It pits you and other Roblox players against each other ...