I've tried several of them, whatever I can find and they all work great for me. Like xxx said, you really just need to keep it clean and scratch free (get rid of bugs and waterspots)... I like microfiber rags!
Try washing the bike and Purple Slice on the chrome. that is all you need it the chrome is clean. I only "polish" the chrome if it needs it which is almost never.
IMO the very best stuff is Never Dull, comes in a can all ready in pads, simply wipe the chrome with it wipe it off. Leaves chrome looking awesome. Used it in the Navy 40 years ago and still use it.
I picked up some stuff from a bike show recently. I haven't tried it yet, but it is supposed to be pretty good.
It is Master Formula, Metal Gloss for cleaning chrome, aluminum, stainless steel. Then it has a second bottle called, Metal Sealer Gloss that you put on to protect.