No Hamilton would not be able to win races in a Force India. Although currently the cars are as close as ever, there is still deficits in performance between cars. There is nothing wrong with this, it is part of the sport. If you want to watch pretty much equal cars go and watch A1GP. F1 is about competition between teams, not solely drivers.
What you have to do is judge each driver's performance against his team mate. This gives you an idea of his capabilities. In some cases drivers can be favoured by teams, but nowadays they will always get equal machinery and engineers to their disposal.
However, in a Force India Lewis Hamilton would outperform Sutil and Fissichella. He would probably rack up a few points. Who knows, in a wet race he may go even further than that. Many Hamilton haters use the excuse that Hamilton has had a seat in a top car from the off. True, but judge his performance against Alonso last year and you see he is an extreme talent.