Nao, For the flames to engulf the forums...
Let us compare the games
Community: Roblox has one the size of Russia and Canada merged together. Blockland has one the size of a small hamlet (Tiny village).
Gameplay: Roblox is more about 3rd person shooting. Blockland is more 1st person.
Building: Roblox and blockland have the same, But Roblox can C-Frame and make bricks float without having bricks under it.
Servers: Blockland ones are only up when the owners in it or if dedicated (Dedicated ones tend to blow) Whilst roblox servers are always up (Unless the owner chooses to close it).
Creations (Models): With roblox it is relitivly easy to make a weapon, You build it then shrink it... Then add a script. With blockland it takes a forget load of modeling with expensive or difficult to use programns with a tonne of scripting.
Site/setup: Roblox has a full site with economy, comments and a tonne of stuff. Blockland has the default nothing and a bit of RTB if you want it.
Overall: Roblox 5, Blockland 1. Nao, Let the flaming commence.

Note that I have played both games, so I judge fairly. Also, My roblox is still working fine and my Blockland recently broke, With Badspot giving me the advise when I said I need some OTHER help. friendy programn never started up, Key glitched like hell and thinks I still have it in even though I removed it when I un and reinstalled blockland.