I have only ever owned the latest out of the Nexus phones, so I can't say anything as far as performance or build quality is considered.
But in terms of industrial design, I think it goes Galaxy Nexus > Nexus S > Nexus One from best to worst looking.
I think the Galaxy Nexus is very mature and classy looking, one reason I decided to move from SGS2 to the SGN. The Nexus S looked okay but somehow looked like a bastardized Galaxy S phone. I thought the Nexus One looked really funky with the mismatched paintjob and overly rounded corners.
I have to say the Nexus One is probably the best built of them all though, I'm pretty unhappy with the rear cover on the SGN - I was happy with the rear cover on the SGS2 because even thought it feels cheap it actually wasn't... the SGN flexes in the center of the rear cover, and the Google logo on the back isn't entirely flush which makes it kind of weird to hold if your finger is rubbing on the logo.[COLOR="Silver"]
Phones: Ericsson CA638 > Ericsson KF788 > Nokia 8260 > Ericsson T68 > Sony Ericsson P800 > Sharp GX32 > iMate JAM > Moto RAZR V3i > Samsung U600 > Samsung Omnia > HTC HD2 > Samsung Galaxy SII > Samsung Galaxy Nexus
Tablets: B&N Nook color > Asus Transformer TF101 > iPad 2