I think by default a onrail shooter is being half assed if you are developing for a console/pc. Yes ofcourse it does not mean it has to be a bad game made as cheap as possible but I do see it as a big indicator that somebody was not willing to go all out. Afterall a onrail shooter means you can save time and money on the lenght of the game to begin with. I believe RE:UC was around 6 or 7 hours and that is by far the longest onrail shooter on Wii, less than half of Dead Space. Also you can skip on what you do actually show as you are the one deciding what the player will see so no need to build your levels the same way as when the player can walk around.
Onrail shooters belong in a arcade. Once in a while a console onrail shooter is nice but there is no deining that on Wii its only done because devs/pubs dont want to spend the money to make the game like they would have done on pc/x360/pc.
Because at the end of the day when I have to spend my 50 or 60 euro's and I got the choice between a onrail shooter which will be far less long, will allow me far less freedom and gives me less replay value or a other game which takes longer to complete, lets me walk around and gives me more replay value as I can explore more than the first run for me, and probably alot of others, that is a easy choice. If its a populairity thing than why dont we see onrail shooters on x360/ps3? Because its a money thing. Still no real money for Wii so they still need to do it as cheap as they can. That is why the Wii already has more than half a dozen onrail shooters and the others consoles dont.