Hi,
there are so many places to visit in India that I would recommend you don't look at India as a whole, but pick out specific regions with their particular local history and cultures. Think Europe without the borders!
Of course you will want to go to the Taj Mahal and all the really famous sites. But it depends whether you want to get to know the country itself or only the postcard-places.
I think that the Indian subcontintent has some of the most beautiful places in the world. I prefer visiting the cities like
Mumbai,
Bangalore and
New Dehli - depending what you are used to, you will be flabbergasted by the sheer size of the cities and the economic and cultural scope!
The first time I was in India I had all my preconceptions swept away. For me the subcontinent was a mixture between media reports on slums and ghettos and the fake mysticism transported by the hippie-movement.
I became so infatuated with Bangalore and surroundings that I even considered buying a house there and settling down. Unfortunately purchase of property is reserved only for Indian nationals. But who knows? Perhaps I will marry a nice Indian man (*wink*wink*).
Sorry for the long vent...
Shanna