In my opinion, Mr. Amitabh Bachchan has the best accent and being a famous Hindi Poet's son, he definitely has the best Hindi too.

Aishwarya rai and ABHISHEK Bacchan

That legend is no more with us. I don't know you heard or not but once you hear that voice you can better judge. "चिनॉय सेठ जिनके घर शीशे के होते हैं, वो दूसरों पर पत्थर नहीं फेंका करते" -राजकुमार

For some reason, I really tend to like Katrina Kaif, not only she's gorgeous but also has a very cute accent.