Rainbow's Down to Earth is up there with all the Ronnie James Dio albums except for Rainbow Rising. Listen closer to the songs, they were very well written. An example is the choir-like backing vocals in Since You Been Gone, which help elevate the track to a far more musical level than any of the uber pop drivel of the Joe Lynn Turner years.
For songs, Eyes of the World is without question right up there with Man on the Silver Mountain, Stargazer and Gates of Babylon, and Danger Zone, Lost in Hollywood, and Love's No Friend aren't terribly far behind.
Graham Bonnet was a fully adequate replacement for Ronnie James Dio (and this is coming from a lifelong, voracious fan of Dio). His performance is completely original and individual, there's no one who could have delivered those vocal melodies as well as Bonnet. Blackmore mostly toned down to speedy playing on this album, but there are tasty bits all over here, easily matching Van Halen, Ulrich Roth, Gary Moore, and Michael Schenker as the best of that year.
To compare this with the '80's Rainbow is to do this album a terrible disservice. This was the last Rainbow album, period.