I seem to remember that the Daily Mail (normally a great BA hater) ran a comparison between a BA flight to Barcelona and a Ryanair flight to the same destination. Initially the Ryanair flight seemed a far better deal. However when factors such as proximity to the actual destination, baggage fees, check-in fees, seating etc. were factored in the BA flight actually turned out cheaper.
There are pro's and con's to both, I don't think you will see the dinosaur/legacy carriers drop as quickly as many people would like to think because you cannot run a full scheduled long haul service on the LCC model. There and back day trips to Sao Paulo don't work and even O'Leary himself was quoted as saying he would never go longhaul as he didn't want pilots lounging about in hotels at his expense.
There will always be space for the two systems especially as long haul requires the feeder airlines and routes. It is not until you need this structure that the 'fixed' carrier benefits become apparent such as the overnight accommodation and automatic re-booking to the next available flight. Through booking for long haul with a legacy carrier will always offer a better service should it all go wrong for whatever reason.