well... i use ruby because:
a) im 15, doing GCSEs and dont have the knowledge or time for more complicated languages
I don't think you'd have very much difficulty switching between scripting languages. The syntax may be different, but there are equivalents for the most common commands (I have minor experience in Perl, GML, Javascript and Python)
b) Ruby is the greatest scripting system ever...
no really... everything is an object so by putting hello.upcase for instance... hello now = HELLO or hello.size returns 5 because its 5 letters long...
Unless I'm sorely mistaken, everything is an object in Python as well.
"hello".upper() also returns HELLO. "hello".capitalize() will yield "Hello".
c)the ruby interpreter already uses a cut down version of SDL and the interpreter that needs to be packaged with your games / scripts is a measly 0.5MB, so that plus your 1MB of script = a game at the smallest size!
Is the size of the game you're hoping to make really that important? Between the massive hard drives in computers and the popularity of high-speed internet, I'm not sure why it really matters if a game is a few megs smaller than it would be.
e) ruby is quite fun to program because its so dam simple... i found gamemaker harder than ruby... and ruby is raw code XD
Gamemaker is really pretty easy, although I've always had a little trouble with it. And you can do raw code in gamemaker. Just create a script to be executed when an event occurs. GML is pretty easy to pick up.
im happy with this one and my ability is quite high with it... thast the reason im trying to break barriers and build a complete game engine using a lagless simple ruby audio / graphics system... already built into RGSS.
Well, that's your prerogative. If you want to be the first to do something big like that, go for it, but if you want to make games as a hobby, you might be better off changing plans.