Totally agree the first flight sticks in my mind because of the excitement of the occasion but also the beauty of the aircraft.
I was a young 17 year old working in the Cargo Centre at Manchester Airport, BA ran a trip for agents down to Heathrow for an exhibition and my employer sent me along for the ride.
The aircraft was the inbound JFK flight which was positioning to Heathrow for regular maintainance. I recall walking out on to the ramp to the fantastic site of the VC10, the organiser of the trip knew it was my first flight and arranged for me to sit up the front. A magnificent day, spoilt only the the fact we came back by coach.
Last year I flew the first time on the A380 from Manchester to Dubai en route to KUL I confess also to have fallen instantly in love with that aircraft.