I love his voice, but yes, he had his best voice in 87-89, no doubt about it. Yesterday I watched the Boston DVD (which I love) and then the Rattle and Hum DVD....... well, the difference is huge, so much more power and clearness in his voice. But he was 27 and wasn't smoking that much..... now he is 45 (soon) and has been smoking for more than 15 years..... you can tell. Still, compared to POP era, it's better now.
Peace