Because he programmed game play routines a lot and dealt with everything involved (i.e graphic rendering and such) more than the average Joe it looks like he is a good programmer because he just shakes it out live on some streaming website. Those concepts are language-agnostic and you can remember them.
I recommend you build a game of similar scope before saying stuff like this.
I know tons of people, myself included, that have coded something of similar, if not bigger scope than Minecraft. The only difference between Notch and everyone else is that Notch ended up creating a game that became extremely popular. It is a combination of skill and luck. Thinking it is all skill, and even worse, thinking that you are "gifted" because of such a happenstance is very unhealthy.
Also i hope you realized that you responded to jonathan blow, creator of braid and a gifted programmer himself. Atleast give notch some credit
Pics or it didn't happen. Merely writing something with an equal or larger amount of LOC doesn't count.
To me, being able to sell (not give away, charge) thirteen million applications that you write is a testament that you are good at programming.
Now, "programming" has many different dimensions, but Notch achieved something that very, very few developers will ever able to achieve in their lifetime (I'd argue he's actually the only solo programmer who's ever been able to achieve such a goal, beating even icons such as John Carmack).
Let's be perfectly honest, after Quake 3, nothing id put out was really fun despite all the technical achievements Carmack made with the subsequent engines
I'm not saying Notch is a bad programmer, I admire him very much, but you need to keep the success / marketing / fun factor separate from the actual code