Spitz set his records in the 70s. Its not like they didn't know about silicon and plastic, so it was his choice to swim sans or cap goggles and with , as you call it, a "rockin' mustache." He did the same thing Phelps has done today...dominated every event he swam in, against the competition of the time. Phelps has just done more, and will probably beat the record of records.
I think in terms of pure olympian, Phelps is the better swimmer. Even without the NASA suits the guy breaks records (I've seen him swim in meets as far back as IIRC 1996-8 when i swam for one of the clubs that had meets against NBAC). He's been a monster since he was 12. The nutrition, workout routines, and cross training these guys do counts for the massive improvements over previous records. Olympians from the 70's would collapse at some of the workouts these guys put themselves through. The suits and pools give that extra .09 second boost over a 50. Maybe half a second over a 200M (granted, a lot, but these records are being smashed by 4, 5, 10 seconds as the distance increases...thats miles in a pool). The rest comes from hard work, and increases in scientific knowledge of anatomy and what makes us tick.
It's not like they are breaking spitz's world records...the records have been getting broken for years over and over again. These guys compete at the pinnacle, and push each other. The olympics just brings these records into the public eye. Unless you keep up with swimming, you don't realize that every meet that brings out world class talent will probably set a new record in at least one event, maybe many more. Doesn't cheapen the fact that they are still the fastest guy in the world...for now.
Until you've gotten up at 345 int he morning for a 430am club workout, swam an 8-12k yard workout, gone to school, then gone to your schools practice in the afternoon for a nice little warm down school practice of another 5k yards, don't knock how hard these guys work. They deserve the records.