What screen resolution on Android has the most apps and games?

Q. I'm planning to buy an Android phone but my budget limits me to phones with 240x320 resolutions. Now, I'm a bit hesitant to buy such phone because I think that it has the most limited number of apps and games available. Yet, I really want to buy an Android as soon as possible.

A. The Android Market has more than 3,00,000 apps but rationally thinking, how many of these apps are actually worth a download or are actually gonna be used by you?
The resolution you specified supports are lot of the useful apps out there and you won't miss out on anything big.
so i think you should go ahead with your purchase.

How can I convert an executable to a format Android phones can read?

Q. Most Android applications are written in Java, but I will use something else... I have no trouble of making the EXE file but can someone please tell me how to convert it to a file Android can read?

A. Android system does not understand PE format. so called windows exe files are in this format (PE stands for Portable Executable but it is not so portable after all!). likely Android executable frmat is ELF, a well-known widely used (among several systems) "codes container".
moreover, the code into windows executable files is for x86 processors (or for CLR, not JVM), and Android hardware for sure has no x86 processors and afaik no x86-opcode compatible processor too.

so basically, it's nonsense "converting" an exe (specific format, specific system, specific machine code for specific processor, specific library bindings) into "a file Android can 'read'" (oh, as passive data you can transfer the exe to android as it is, but forget it can run it or even "see" that there's code inside! just data to it!)

What is the difference between Android Operating System and an actual Droid?

Q. Obviously, a Droid probably uses the Android OS, but I know that some phones aren't actually Droids, but use the Android OS. So, what is the difference in what I am going to get with each product. Is either better than the other. I am specifically looking at an LG Optimus S, but didn't know how this would differ from a Droid.

A. Actually there is no different when each one has Android system. Droid is only fror CDMA.