Its different from show to books though, Robert is much more likeable in the show.
In the books, he is, basically, a lesser competent Henry VIII. A child-murdering, superficial bully that turns into a bloated pig.
I'm a huge admirer of the Targaryens in the book, so disliking the Lannisters is much appreciated.
Despite this - Jamie had his valid reasons for killing Aerys II. as he was going to melt the whole city down with wildfire.
Who is your bet on the next one to be slain?