Other than 'higher-the-number, better-the-quality' (usually), they're consistently good.
Sometimes, tho, body wood may be the only difference between model higher/lower numbers.
Sometimes older/newer versions of the same model number use completely different woods/ pickups/ preamps.
For example older SR505's were all maple, active pickups, and had mid-sweep in preamp, while new SR505's are (mostly) mahogany body, more than one neck avail, passive Barts, slap/switch in preamp.
All depends what you're looking for.
Browse this catalog archive: http://www.ibanez.co.jp/anniversary/index.html