People talk about his success for Argentina and Napoli between 1986-1990 but was that really his peak? Having watched lots of clips of him over the years, he was more spectacular from 1980-1986. Faster, leaner, more agile and a bigger goal threat, not totally addicted to drugs. Able to beat defenders with ease and leave them behind. It's a team game and although 1986-1990 was his peak trophy wise I believe as an individual he was better from 1980-1986. Which makes the whole 'one man army' description of him at Napoli seem ridiculous. Napoli cleverly built their team to be stronger year by year.
In Barcelona he used to play all in all as a striker. Take a look at available footages and you'll see vast majority of his goals for the blau grana where quintessential striker's goals. In Naples he would be in charge of much more playmaking duties, much in the same way as in Argentinian NT.
Probably 1985 calendar year (day by day) and 1986 (World Cup, that is basically his 1985 level but more focused and fresh, preserved for the tournament), extended version goes till 1988, but he had some decline post-WC 1986, physically. 1979-1982 level is a level below it imo, despite the stronger domination in his home country league, WC 1982 and early Barcelona days.