OK "son" I will...
Gayle became established in the side in 2001 (out of 65 games against Test-standard sides since then he's played 58, all 7 missed through injury or punishment). Since then he's averaged 38.83, fairly impressive you might think. Well, no, not really. For starters, consider the effect the 317 (dropped on 80) has; had that catch been taken it'd be 36.52, still decent but less impressive.
Now actually look at the scores. As a short-term example, consider the recent England tour; 77 for once out at Lord's, when England's attack was a shambles; 11, 13, 23, 16, 28, 52 later on once Sidebottom joined the side and the attack improved. Then consider the Pakistan tour before that; did little at Lahore and Karachi when there was a bit in the surface, and scored 93 on the pancake at Multan.
This is symptomatic of a general pattern of Gayle's career; often pretty good against rubbish attacks, rarely showing-up when there's some decent seam and swing bowling around. I CBA with going through his entire career, but it's very obvious that his heaviest-scoring series (Zimbabwe 2001, New Zealand 2002, South Africa 2003\04, England 2004, New Zealand 2005\06) have come on pitches that have mostly offered little to the seamers or spinners and mostly against teams with wholly mediocre bowlers.
Sherwin Campbell on the other hand averaged 35.83 in his first 43 Tests when a weak attack was a rarity. Though he cashed-in big against the weakest bowling he faced (New Zealand in 1996) and also had more than one lean patch (going 14 innings without a half-century in 1996\97 and 1997, not always against strong attacks; and 10 - inclusive of being dropped - in 1998) he still scored any number of valuable innings against powerful bowling-attacks, from his debut in New Zealand in 1994\95 (51 and 88 against Morrison, Nash and Doull), to in England in 1995 (69, 2, 5, 93, 79, 10, 44, 47, 16, 89 against Fraser and Cork), to Sri Lanka in 1997, to (probably most of all) Pakistan in 1997\98, then finally Zimbabwe in 2000. He also played excellent innings against Australia in 1996\97 and 1999, New Zealand in 1999\2000 and England in 2000, while not managing to maintain consistency throughout the series.
The Barbadian right-hander was easily the better batsman in Tests than the Jamaican leftie.