There are several serials with a protagonist applying out of the box techniques to solve crimes. Somehow they take inspiration from Sir Arthur Conan Doyle's iconic Sherlock Holmes. He has a particular sentence which he keeps shouting about, 'You all see, but you don't observe'

The mentalist is on the same lines. There have been many and I'm sure there will be many too, but this sets a different place in viewers mind because of the back story and execution.

Each one of us has a frustrating part which believes if the criminals don't follow rules, then why should the police, they should be given free rein with all the unorthodox methods for finding the culprits. The mentalist gives this particular emotion a vent. The lead of this series, Mr Patrick Jane is very well versed in hot reading, cold reading, manipulation, keen observation, deduction etc. Though he uses these skills to help the Police solve crimes, he has an open agenda of revenge. That's something that connects him with the audience. He works with Detective Lisbon, the formal head of the team. She being a girl adds the balance on screen.

Do not go expecting mind benders and complex plots. There scarcely are any thrilling moments (Go see Sherlock for that) The show wins in terms of execution. The relations between fellow team members. Relations between Jane and Lisbon are convincing. Patrick Jane acted by Simon Baker is the most pleasing of them all. His charming, playful demeanour seals it for me at least.

to summarize, the following things make the show a success.

A lead character with a tragic back story that connects
Execution and inter-team relations
Mr Simon Baker