Well, here's a quick review on all 3 starters:
Bulbasaur: Probably the best pick for early on in the game. Bulbasaur will help you do well against the first two gyms (Brock with a 4 x advantage, Misty with 2 x advantage in terms of damage), and turns into a very powerful and versatile Pokemon that can do a lot of roles in competitive battles - attack, annoy, mega heal. I'd say he was the easiest of the 3 starters to use because of the early advantage, and has only a weakness to one gym (Blaine's Fire Gym). Ease of use: 6/10
Squirtle: The mid-ranger. Can do well against the first gym, but evens out towards the middle areas, and is bad to use against Surge and Erika. Overall, it's a good tank that can take lots of damage, and dish out a considerable amount as well. Ease of use about 7/10
Charmander: The hardest to use because of his heavy disadvantage to the first two gyms, Charmander gets better to use later on, and owns totally against Erika. I consider Charizard to be the most powerful of the three starters, if only for the fact you can breed Dragon Dance onto him :-). Despite that, he's not easy to use, and his type makes selecting moves a little tricky. Ease of use: 5/10.
So, overall - pick Bulbasaur if you want an easy start, but Squirtle is the easiest to use through the whole game. Just my coupla coins on the matter