How hard is it for a single programmer to write a game that's not to complex, not to simple?

Indie developers make all this great games in such a short time maybe about 2-3 years, and make it across multiple systems. I've always wondered how they did it. How hard is it for an intermediate to advanced programmer to make a game like minecraft, castle crashers, super meatboy, binding of issac, blah, the old version of super Mario 64 ( I know it wasn't developed by a single developer) how long would it take them to make each game, and how hard?

I'm indie developer for the iPhone (https://www.kickstarter.com/projects/294438488/draw-me-that-for-ios).

I have six iPhone games (counting free and paid versions of the same game separately).

The trick for me was A. Teaching myself how to code. I bought a book and watched videos online (Big Nerd Ranch and iTunes U). B. Focus. I spent a lot of time thinking about game ideas, and a lot of time coding and refining. It helps to have feedback and get ideas from friends and stuff.

For me it took a couple of months (given that my games are rather simple) and it is taking me a longer time with my current project. For more advanced programmers it really matters about the scope of the project. For something like mine craft it would take a much longer time, while a game like 2048 was made in a weekend.