I find the responses to this to be a little bit surprising and very interesting.
Going faster isn't the "only" thing. Comfort, reliablity, braking, saftey, etc. etc. are all very important.
Even if there were ZERO improvments to bikes in the last 5-10 years a new bike would be "better" because as others have mentioned they are brand new and not worn. Everything works like it is supposed to. Everything has grease. All the gaskets seal. All the rubber is new and not cracked.
Now add to the mix the upgrades in suspension, brakes, carbs, powervalves, ergos, etc. and you have a much better bike.
While many of these upgrades over the years won't always shave time off of your laps they will make you bike kick over easier, jet more smoothly, foul less, have a wider powerband, and make the bike easier and more fun to ride.
So there are many reasons to go to a new, or newer that will probably be faster and a whole lot more.
.02$