Is that because of the technical achievements that Carmack has done (Carmack's Reverse, Fast inverse sqrt, etc.)?
You still have to give it to Notch for showing that you can make an extremely entertaining game while not pushing any hardcore boundaries, such as graphics. Perhaps this will inspire more people to get into software development.
More due to their attitudes towards source code and supporting a new generation of developers (Notch pays lipservice to open source and claims to be an avid supporter of the Pirate Party and an opponent of IP law yet aggressively pursues any competition that resembles Minecraft in any way with legal threats)
In terms of actual code they're not even in the same league so I won't bother comparing anything Carmack's achieved with Notch's magic number and circular reference-ridden Java code.
You still have to give it to Notch for showing that you can make an extremely entertaining game while not pushing any hardcore boundaries, such as graphics. Perhaps this will inspire more people to get into software development.