I want to make a pretty simple game for the android and iPhone but I am not entirely sure where to start and what I need to know so could someone point me in the right direction? Thanks.

So C# would be the best to learn?

Based on my experience, I would suggest that even if your goal is a long-term career in programming, definitely start off with GameMaker.

If you're a total beginner, it's a great place to start. It has a lot of "drop-and-drag" stuff (for people who don't know code yet), but if you want to tap into its full potential, learn GML (GameMaker's own little "programming language"). That's a good way to get acquainted with programming basics (variables, arrays, loops, etc). It is also an "object-oriented" system, so when you get into "real" programming languages you'll already understand some of the basic object-oriented concepts.

The other alternative (learning a "real" language from scratch) can be a total pain and hardly worth it for a simple game. GameMaker abstracts away a lot of the annoying little micro-details needed to do basic stuff like playing sounds, drawing graphics, etc. and in my experience with Java these things are unnecessarily overcomplicated. I think I've learned them pretty well, but if I had just gotten into Java with no previous experience, I think I would have given up a long time ago (lol). For example:

// GML:
sound_play("boom");

This is by a longshot as easy as it gets. It's straightforward and the intent is clear: play the sound "boom" (lol).

// Try to do the same thing in Java:

import javax.sound.sampled.*;
import java.io.*;

public class Sound extends Thread {
	public AudioInputStream audio_snd;
    	public Clip audio_clip;
	public String address;

	public Sound(String address){
		try {
			start();
			this.address = address;
			audio_snd = AudioSystem.getAudioInputStream(new File(address));
			AudioFormat audio_format=audio_snd.getFormat();
			DataLine.Info info = new DataLine.Info(Clip.class, audio_snd.getFormat(), ((int)audio_snd.getFrameLength()*audio_format.getFrameSize()));
			audio_clip = (Clip) AudioSystem.getLine(info);
			audio_clip.open(audio_snd);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	public void playFromCurrentPosition(){
		audio_clip.start();
	}
	public void play(){
		audio_clip.setFramePosition(0);
		audio_clip.start();
	}
}
class soundPlayer {
    public static void main(String[] args){
        Sound boom = new Sound("sounds\\boom.wav");
        boom.play();
    }
}

It took me Ages to figure this out, and I still don't quite understand every bit of it. But I made it work; that's the main thing. But to get there, I had to learn not only the basics of Java but also how to work with all these other things (AudioInputStream, AudioFormat, DataLine, FloatControl, etc.), all just to play a sound. I've had similar experiences with the web (JavaScript can do a lot these days, but sound is still a little tricky), and I'm sure Objective-C, C# etc. have their fair share of extra work to manage the basics as well. And don't get me started on getting the AVD (android emulator for Java) working for the first time! : )

And besides, Game Maker has a lot of potential (and apparently even more since I last used it, to the point where it can supposedly create games for every platform known to man, including Android and "iThings" (love that btw)). I once developed an entire "console" type system - a program that ran my games from CDs (like the PS3 or or Xbox). It had built-in joystick support, two-player games, and all kinds of cool little extras. GM can also do multiplayer games, though I never experimented with that. And they have a free version, so you can try it out before you go and buy the full package. I could go on about this, but I think you get the idea. : )

Anyway, I hope this advice helps; I started off as a total noob, not knowing squat, and while I've still got a lot to learn, I've come a long way; and GM helped me get there.