Of course S2 is not a high end game but you don´t have to reduce the amount of polygons (especially for the arms and the head) that much.
S2 (and even low end computers) wouldn´t have any problems if you double the amount of polygons in these areas and smooth them. That way it would look better.
And you should also think about using a higher texture resolution. Nobody expects a perfect model here but in my opinion this should be improved.