That is a very good question
I suppose it all depends on individual taste for example Nick Cave world wide star i don't like his voice but hey other people think diffirent,
I am of the opinion that you don't have to have a large vocal range to draw someones ear it helps though if you can sing with feeling and some depth not even the biggest and best get it right every single time
First thing is we have to establish can we sing?
for this there has to be a certain amount of honesty, so many folk have the friends that will tell them they can when they can't
This is nither good for the performer or the audience, we have to concentrate on what talent we do have if thats guitar or anything else then work on that instead of waisting valuable time
Secondly, we may have a good voice but lack of belief can make us bieleve otherwise
confidence can play a big part in a performance, nerves can and will make for a weak perfomance only way over this is to go out and do it
finding your range and singing within that range is allways best, gaining some knowledge of how the voice works, how to breathe etc is a big advantage
Recently i have taken some vocal lessons learning how to do vocal exercises scales etc pushing my range to see how far i can go
it has enhanced my vocal performance no end
Somthing that lots of people fail to consider is Backing vocals there are those who may not be able to do a full vocal performance but can do backing vocal, backing vocals when done well can be the making of a track