Bombay!!! What can I say! Just that there is no other city quite like Bombay in the entire world!!!
First of all Accessibility: Bombay has to be the most accessible place in India, at par with probably New Delhi due to the fact that it is connected to different parts of the country by different means - it is the headquarters of 2 different Railways: the Western Railway, and the Central Railway which run through the busiest and the most important areas in the country
Next Entertainment: Here I think probably Bombay beats out New Delhi. Lots of places where one can go sight-seeing. In addition, lots of Multiplexes, and Malls. Beaches. Gardens. Highrises. Drives. Sports. Sea-Shore line. Eateries. Discos. Pubs. You name it and you got it - right from the very glitzy and expensive ones, to the normal one small room bars selling country liquor.
The Culture: Probably the best part of Bombay for me is its culture. Having been to various parts of the country, and visited cities like Chennai, Delhi, Ahmedabad, I can vouch for this. The Bombay culture is unique in all of India. People from different parts of the country have got so assimilated that it is difficult immediately to tell who is who!
A very equable climate - neither too hot, nor too cold (though does tend to get stuffy during summer and monsoon), affordable food, easily availability of residential places (though bit expensive), availability of jobs if you are willing to do anything, all this make Bombay very unique, and give it a totally different flavour. You have to visit it to just experience it. As someone has said: You either love it or hate it, but you cant ignore it.