What your first game should be?
I do not think, that anybody asks this question before diving into game development, because if you want to make a game, you already know what game you want to make and this is the problem.
Do not pick too big. I saw a lot of people picking games like Quake, Doom, Half Life... Maybe somebody wanted to make Age of Empires or Star Craft (I did not met any one who wanted and started making strategic game, I wonder why?) but these games are way to big. To be fair even Battle City is too big as your first game.
People who picked too big games say that they learned a lot and this is understandable because you have to justify why you wasted two years of your life and still haven't made any working games, but the sad truth is that your learned shit. Yes, I am right and you are wrong. How do I know this? Because you been solving the same problem for two years!
Do not think anything original. Let's be very clear: make a clone. It is very rare that people understand how games mechanics works before they start making games. If you think that you are genius (most likely you are not), you try to make something original and in the end your game sucks: it is hard to control, it has no purpose and nobody wants to play it.
So you what your first game should be? I say – cards. Why? It is small enough. It is hard to screw up as you can always look for the rules on the net. It has some moving parts and need some animation, but not a lot. It has some logic but not too much. It has some interaction, so you need to make basic controls. Do not know any card games? Try http://worldofsolitaire.com/
My first game with Phaser was a solitaire and I have to say that it was more challenging than I expected. Of course, I made it in one week, not in two years. I promise to talk about it in feature articles.
My first-first game was not a solitaire. It was a clone. Original game was 2D and had only 3 levels. You had to control submarine and sink the ships floating above you.
To make a game I had to:
Make keyboard (mouse) controls,
Ship floating animation,
Collision detection (bullet and ship).
Essentially the same I had to make for the card games. So if you do not like cards, there are simple games you can make.