Have to agree with you as I have seen many bad guys leading great life till the end. Of course there will be counter argument that their happiness is superficial and they do not enjoy true peace and joy. I think the Chinese fiction, "Ah Q" by Lu Hsin best explained how the idea of karma come about. When Ah Q cannot defeat a big bad bully, he will find ways to appease his inner anger and frustration. Hence, the thought of karma, heaven will punish the bad... will make him happy again and Ah Q was always a happy guy..... I sometimes wonder if there's karma and is it only dumb ones who try to be good....
Again, some will say that there is indeed karma as shown in cases like Saddan Hussein, Gadaffi... Well their endings may not be the results of karma but more of obsession for power, control ... If these guys quit at the peak of their career or chose to give up power, they will still be having a good live now.
Just sharing my thoughts.