Firstly, check out my profile and shoot me a message sometime. I'm always willing to help and coach fellow coders, I'll spare all the other readers of this thread my credentials and experience by just saying in short I started as a freelancer and have evolved to the point where I have some very large clients and I now work from home coding for money. My statements are always a bit different than the popular consensus but they are real world applicable (people actually pay for things I say, things I make actually get used and so on). Sorry if anyone takes this as bragging just want a little quickie that of who I am and why what I say might be helpful.
Now on to the actual question, TETRIS! It always seems that tetris has nothing to do with "real" games but it actually teaches you lots of the fundamental rendering techniques and issues that you will be dealing with in more complex projects. Make your own tetris clone, from the sounds of it you should be able to hammer through it pretty quick and not even really notice how much your learning as you go.
Next, MARIO! Don't do mario first, tetris will actually be the one that teaches you the collisions, positioning, translations, rotations and all the good stuff that enables you to expand into more advanced games. The idea of mario is where you will actually start learning sprite states, ai and world dynamics. You learn how to tell when mario is jumping, if he's little, big or has a tail, how to make the enemies "think" (yes it sounds stupid but they still have to "think" to patrol a small area.) This will carry over more than you realize, coding an NPC to patrol is pretty much the same in every game, you assign nodes that the NPC would travel between, select one that is closes to the current position, translate to it (move) and continue. In later projects you will just extend upon this knowledge to also "look" for the player, charge, shoot or what have you.
After those two you'll actually have a pretty good grasp on most of the core fundamentals of game programming and can probably go ahead and get into visualizing your text game. If you want to push your experience and knowledge a bit farther before moving into a real project go zelda! Zelda (the old snes version) is actually one of the most advanced 2D tutorial projects you can make. It incorporates stats, items, more advanced AI, keys, quests and conditional events, dialog and lots of other minor things most people never notice.
So, in short that is my suggestion for your direction. Tetris, Mario, Zelda clones. Like the old adage goes, you must first learn to crawl before you can walk. The text based game you have built is great for learning how to program but there is still a lot you need to learn about core game development techniques before you can really go jumping into making something of your own. These three games are pretty easy to clone and will teach you a lot more than you would think. They will also start to show you the importance of having a known design before getting started. (Which possibly is even more important than actually knowing all the little animation, collision an AI tricks).
