I'd say top 20 esp if you factor in his intangibles that you don't see in the stats like leadership, longevity and competitiveness.
i say not top 50. kevin garnett is part of the unholy trinity of trash along with bruce bowen and carl malone. they will get no accolades from me. f*** them all. barkley >>>> malone & garnett
Name 20 players who could "dominate offensively" like you claim....and could also impact a defense in a way that KG could. The only players who I would confidently take over Garnett on defense are Russell and Hakeem.
Russell Kareem Shaq Robinson Duncan Dream Wilt Karl Malone Lebron Dr J Jerry West Jordan Magic Durant Dirk Big O Bird Isaiah Thomas Moses Barkley Stockton Those are 21 that are better than KG, just the top of my head.