Portals, useful for fast transport. There is a lot to benefit from by being able to go from point A to B instantly in Minecraft, you just have to think with portals.
Minecraft is a game as much as Simscity is a game or Pokemon. You get on Minecraft, make friends, gather resources and build whatever you want. Everyone's goal in Minecraft is different, yours may be to grief someone's fort while yahtzee's would be to make a giant d- out of gold blocks. Graphics-wise, its default texture pack is better than pokemon or any other "light" games. Comparing to a "heavy" game like Just Cause 2 is just unwise. It's like comparing xbox games to iphone games, both are equally awesome in their own unique ways.
Also, did you buy BFBC2 when it was $6? If not, compare THAT to Just Cause 2. Talk about a cheap deal.
When modding Minecraft, you need knowledge with JAVA, a programming language that's very applicable and one of the most widely used ones too. Basic/barren? Every engine is basic and barren, just so people can add on to it, if it was already jam packed with goodies, there wouldn't be a need to mod.
It is true that the devs are happy to support modders so please, remember your side of the argument, devs at Valve and pretty much any game (BETHESDA, I AM LOOKING AT YOU) supports modding of their games.
Wikipedia of Games Award goes to Fallout 3/NV/Oblivion... freaking Bethesda games aren't good without mods at all.