Actually, I must agree with most of the answers here, Kerala is definitely great. As for me + my friends from Europe, we mostly enjoy Goa. It does not have all those great buildings and palaces, BUT you have REALLY good hotels and the beaches are phantastic. There are also British pubs, and all in all the food is MUCH BETTER than in normal continental India - since at Goa traditionally pork is eaten - so you get lovely spicy sausages even. And - as already mentioned - food has a real variety - it's not just the same curry with a different name on every day - which you get rather sick of after a while.
The native people of Goa are also completely different from those of continental India - they are proud yet friendly enough and in general much better educated. You see no beggars there and no paddlers disturbing your nap on the beach - !
What I also liked were the souvenirs from the Himalayas - really hand made original stuff you can actually wear in European cold winter. The leather work is lovely, good quality...p.e.; not once have I been molested by vendors there, which is a nice change to continental India in general.
Another nice contrast to continental India vacation spots is: the Indian hotel and beach guests at Goa are rather the honeymooning (or pre-honeymooning) kind, which are full of fun but rather quiet- not those huge family hoards with 100 children plus nannies shrieking all over the hotel, stealing sweet food from your table and throwing sand or water at you while relaxing on the beach- well - you know what I mean. At least in our hotel and beach- which was even moderately priced - it was sheer bliss...;
I suppose it's all a question what you are looking for - a real relaxing vacation in one of India's paradises = Goa or- as I presume, there ARE other such places that I've never been to, or a tour through dirty crowded cities - crushed by pedestrians and molested by beggars and paddlers in every step you take, residing at hotels that are none too clean although 5star- and seeing all those "famous sites" trotting behind your guide-which I've also done-and found it rather ghastly!
And to come to a conclusion - India is a continent , and to do it justice, you'll have to go several times to take in just the basics. It also depends if you are going on a spiritual journey or a seeking health - or peace and relaxation- for all this India has famous spots.