Comparing Messi with Maradona, I bet he will never have match Maradona influence and big match performance in the game. But he is far more consistent and far less self-destructive.
To compare their attributes, Messi has better finishing, composure, one-twos and off the ball movement, whereas Maradona has better vision, passing, freekicks and leadership. Their skills, techniques, flair, dribbling and ball control etc. are on the same highest level. So I'd think they are comparable, but since Maradona lead a lesser Argentina team to World Cup glory, and a lesser Napoli to Serie A champion (by far the best league at that time), I would rate him higher than Messi, who has better support and much easier setup for success. (Barcelona may still win La Liga without Messi, or at least among the top 2, but Napoli/Argentina without Maradona is only a "mid-table" team)
Both pre- and post-Maradona they were quite erratic, sometimes mid-table, sometimes top-4. In two seasons with him they finished 8th, in between five seasons in a row top-3.
1980/81: 3rd [16 teams]
1981/82: 4th
1982/83: 10th
1983/84: 12th
1984/85: 8th (Maradona's debut season)*
1985/86: 3rd
1986/87: 1st
1987/88: 2nd
1988/89: 2nd [18 teams]
1989/90: 1st
1990/91: 8th (Maradona's final season)**
1991/92: 4th
1992/93: 11th
1993/94: 6th
1994/95: 7th
...
*universally rated as his finest individual season by almost every Italian paper at that time in their match report ratings;
aggregate average ratings for the 1984/85 season from several publications
7,02 Maradona (Napoli)
6,88 Garella (Verona)
6,70 Tricella (Verona), Matteoli (Como)
6,67 Briegel (Verona)
6,65 Fanna (Verona)
6,63 Tancredi (Roma), Wilkins (Milan)
6,62 G. Galli (Fiorentina), Júnior (Torino)
6,57 Souness (Sampdoria)
6,53 Vierchowod (Sampdoria), Hateley (Milan), Di Gennaro (Verona)
6,52 Galvani (Cremonese)
6,50 De Napoli (Avellino), Scanziani (Sampdoria)
6,48 Platini (Juventus), Zenga (Inter)
6,45 Terraneo (Torino), Bagni (Napoli), Agostinelli (Atalanta)
6,43 Vialli (Sampdoria), Collovati (Inter), F. Baresi (Milan), Volpati (Verona).
In no other season did he get rated over 6,70. So, even in his most consistent season he alone couldn't lift them from mid-table.
The next season they bought Giordano from Lazio for 5 billion lire (Maradona had been bought for a world-record 13.5 billion lire), who scored 10 in 25 in his debut season (Maradona 11 in 29); Ciro Ferrara was making his way into the first-team as a brilliant centre-back; they bought goalkeeper Garella from the champions Verona (the guy rated 2nd of everyone in Serie A the previous season) and brought in the coach that would lead them to success, Otávio Bianchi.
The following season they bought De Napoli for 5.8 billion lire and Carnevale for 4 billion and the rest is history.
**he missed half of that season;
- WITH Maradona: 18 games, 7W, 4D, 7L = 18pts
- WITHOUT Maradona: 16 games, 4W, 11D, 1L = 19pts