good post Yves! )))
Very difficult question...If everybody had an obvious answer,there will not be anymore collection!
I think that the following criteria are preponderant:
A strong image
A story,collective or personal
A classic design which will last in time
an exclusivity
An originality(movement,design)
A manufactured product(LEGITIMITY)
AND first of all,the passion:BUY it if you like it.IF NOT....Don't do it!Watches can be the best or the WORST financial investment!