Whoa, you're getting way ahead of yourselves. You're talking about game subsystems and you haven't even decided on an engine yet. First decide HOW you are going to build your game, then you can decide on the parts after that.
Once you have decided on your language, and platform, you should decide if you are going to be building your own engine or leveraging a 3rd party engine. If you don't use a 3rd party engine, you will have to build abstractions around many things yourselves, namely: audio, networking, rendering, user input, GUI, utilities, as well as a few other things I've surely forgotten. Not to mention, there is a fairly large middle ground. You can use certain software packages called "middleware", so that you can implement your own engine, which customizes the game engine in ways that suit your specific game, but implement generalized functionality for certain parts. As an example, I am building my own engine, but I use FMOD to manage the audio, as that is a particular area that I have no interest in interacting with. However, when it comes to the networking, I have decided to manage this myself, as I don't feel like handing control over to a 3rd party library would make sense for my particular game.
Once you have decided whether you are going to use a prebuilt engine, build a frankenstein (some middleware and some of your own stuff patched together) , or totally from scratch, THEN you can decide how to build your game.
Overall, I would say the first thing you need to decide is how you are going to drive your game's data. Every game is data driven. You have levels, enemies, objects, players, NPCs, ect. You need to decide how you will load these different types of entites into your game. How you will serve them up to the player. And of course, how you will store them so they can be accessed the next time the game is loaded.
Once you have a good architecture for the data driven section of your game, you must then decide how your players will enter the game. Will there be a login screen? Will they start a new game from a selection screen? Will there be options?
Here's all I'm going to say from here: if you've gotten this far and you still want to make a game, come back here. We will help you. But until you have got this far, you aren't ready to make a game.
Edited by metsfan, 29 March 2013 - 06:16 PM.