Hey Sumit -
I too am currently using HostGator and in the past have used Globat, in addition to a myriad of other hosts.
In my opinion it is important that a host has their own servers, managed and administrated by themselves with a
proven track record.
Also, be aware of 'friends with hosting deals'. I once had a dedicated deal with a 'friend', I went on a 2 week vacation and found that my sites (1000s) had been down the entire time (sites with a number of top 10 rankings) and I was completely out of business and actually legally required to owe him money...ouch (6 years later,
)!!
If you are in need of serious, slam 'em hard with traffic, hosting do not be afraid to check out adult related hosting companies. The best in that market can take the hardest traffic you can throw at them. I've had great luck with TechieMedia.net for heavy traffic non-adult projects and they have great support, in addition to that they host a number of sites that eclipse a million unique visitors per day.
Good Luck,
Matt
P.S. I am not affiliated with TechieMedia.net in anyway, I've just had great experiences with them.