I had the same thought when my 10 year old showed me the games he plays on Roblox. Absolutely awful graphics, gameplay, "story", etc, but they are _obsessed_ with them.
It's gotten my eldest son into Lua programing and 3D modelling, so I have no problems with the platform as it currently is.
A few of the games/servers were interesting: Phantom Forces was a reasonably well polished FPS, and the Murder Mystery games (sneaky murderer vs sheriff and villagers, typical social deduction/betrayal game) were pretty fun.
Hoping it doesn't get completely and totally overrun with ads.
I find the platform very appealing even as an adult, as you can script in Lua, and then watch as hundreds of visitors interact with what you just wrote. This week I hacked the Bad Apple music video to run on Roblox, and then had a great time seeing people react to it.
So like flash games that a lot of us grew up with then. There is a lot to be said when the games load in seconds so you can jump from game to game and the novelty value is high.