[strogonoff]

Command blocks and mods aside, Minecraft is more or less large-scale pixel (voxel) art with added elements of (optionally) having to survive while collecting your voxels and being able to program your environment with DIY mechanical/electrical constructions (which could range from assisting own survival to showing off). I personally find these limitations both useful equalizing forces (in multiplayer) and engaging creativity-boosting constraints.

Having seen screenshots of Roblox, I generally find the visuals pretty horrible. Considering its “free to play” model constructed to extract money from players, as opposed to Minecraft’s buy-once-own-forever, the choice seems straightforward.

[strogonoff]

Addendum: for a glance of things achievable mostly in vanilla with enough creativity, check out a montage around the beginning of https://www.youtube.com/watch?v=816mQFkks1Y.