Musician friends have often commented that Ibanez guitars used to be really good. Great tone and necks that could be setup low with no fret buzz.
I don’t think they have that reputation any more. They are still good guitars. But… 
What were the classic years for Ibanez? Which models should I consider buying?
I disagree with your premise. The made in Japan guitars are still really good, such as the Prestige line.
I just bought a 2018, made in Japan, Genesis RG and recently had a used 2017 Prestige RG (which I sold) and they both compared well to 80’s Ibanez RGs that I have played. If anything, the pickups in the Prestige were much better than what you would get in an 80’s RG.
The necks are amazingly nice and they both have the original Edge tremolo. Action can be set quite low, so I don’t know what your friends were talking about. Fit and finish was flawless. They use Alpha pots which are decent.
I can’t speak for the made in Indonesia guitars but I have not heard bad things, other than some people not liking the latest tremolos.
Maybe they are talking about the pre-lawsuit Les Paul copies. I played one once and while it was solid, I would not call it better than Les Pauls that I have played.
I pretty much agree with by-tor. I’ve honestly never met a bad Ibanez. The lawsuit guitars were/are desirable because they’re of the same quality or better as the guitars they’re a copy of, while being less expensive. Their cooler/rarer designs from this period actually go for more than the Fender/Gibson copies.
The later Ibanezs are just as good, just with different styling and features. The lower lines made outside of Japan still have good QC and construction. I’ve seen nothing wrong with the guitars made in Indonesia. The AR series and Iceman series both still call my name occasionally. Hmmm, maybe an Iceman bass…awww, all the ones on Reverb right now are brown.
I played an Ibanez at a local store a few days ago.
It had low action and played great.