Vieri was never healthy 3 seasons in a row.
During Baggio and van Basten time teams would normally score under 60 goals a season, quite an impossible task to reach 20 for players, let alone three years on the trot. Van Basten wasn't far off but got injured frequently.
Shevchenko is an interesting one, yeah, but Milan wasn't always as competitive when he signed and was more in his prime and his numbers started to decrease when they signed Inzaghi and they were sharing goals.
Batistuta on the other hand was a genuine monster and the only focal point of attack but his 20+ consecutive seasons came in his final seasons with Fiorentina plus a 4th with Roma who had an impressive attacking line and scored tons.
Even if you make this number 15 goals or more, you'll miss out some great scorers (like Trezeguet that you mentioned or Abel Balbo) and the list would be modern heavy.