RE: Worst * Pokemon in the TCG
Shining Entei, Suicune, and Raikou work well when you are behind on prizes. Suicune and Entei work excellently for delivering a finishing blow when you have one prize left (or two prizes vs. a POKéMON-ex), since discarding all energies or 10 cards from your deck are negligable. Raikou can't do the same thing. If you have 1 prize left, you use Meta Voltage, and it knocks out enough of your own monsters, the game could go into Sudden Death, or give your opponent a victory if it knocks out everything you have. Therefore, I consider Shining Raikou to be the worst of them all. All of the other Shining POKéMON can be used in specialized decks, but Raikou can't.
As bass_forte mentioned, Ray is the best of the lot. One idea is to use it in conjunction with Mew-ex. Ray doesn't do a good job of attacking normally, but you don't have to worry about that with Mew-ex, since you can just copy the attacks of other monsters until you are ready to use Holy Star. Too bad Ray won't survive the next format rotation...