I think that this thread is as much about something else: Most Underrated Races.
Those who are bringing up Spilak and Porte are really arguing that one week races are underrated, and I agree with them. The achievement in winning Paris-Nice and the Dauphne (let's say combined in one season) might be in real terms comparable to a 2nd or 3rd in the GC at the Giro, but most on the forum wouldn't see it that way. You can't really do anything as a one week racer and immediately be tagged with greatness, whereas there are five monuments (plus the world champs and numerous classics) for one day races, and three, three week grand tours. Personally I'd like to see something like the Tour De Suisse have much more prestige, but it seems to have slipped away from where it was at 10-15 years ago and cannot even compete with the Dauphne....
I like the idea of an almost 'monument' style one week race, but most seem on an even level of prestige (P-N, T-A, P-V, Romandie, Dauphne, Swiss) and suffer from in some ways being prep events for GT's. Maybe something like Paris-Nice should be rated higher, as it's not specific prep for a GT and so even the best GT riders will often hit a mini peak for it, but half of the top stage racers are inevitably lured in by T-A.