covering joint where sheet vinyl floor meets tiled shower curb

Is there a super-long lasting, good looking product that can do this? Typical self-adhesive plastic products just don't adhere long-term.

regular white silicone not good enough? how about installing tile trim pieces?

No, neither caulk nor tile would look right.

In a perfect world the tile would lap down and overtop of the floor. You could perhaps enlarge the shower curb. Or add in an other element like a tile transition or shoe moulding.

Can you post a picture? Maybe some more ideas will come from seeing the pickle you are in...

JW