Don't get me wrong, I LOVED Van Halen at the time. Roth was a great rock star, and Van Halen's playing just blew me away for years until other guys surpassed his finger-acrobatics. I wasn't one who despised the change to Sammy either. I was a long time fan of Hagar from the Montrose album and some of his solo stuff, so I found the collaboration interesting, and I thought Hagar's talent came closer to moving the band from a glorified garage band to a more musical band.
I just always felt that Roth's strengths were just about everywhere but his voice. He was appealing, flamboyant, and he sang with abandon. But once a singer has been around for a while, his audience matures and demands something more. It either has to come from raw musical talent, or from an ability to bring the audience along for the ride for reasons other than musical talent. Roth never had the former, and lost the latter, IMHO.