Only baseball fanatics seem to know how great a hitter he was. He is the best hitter for average since 1950. This is a cut and paste from an article on ESPN-
Since 1950, no batter has matched Gwynn's .338 career average -- not even his idol Williams, who hit .344 for his career overall but just .335 from 1950 on.
Best since 1950:
Gwynn: .338
Williams: .335
Wade Boggs: .328
Rod Carew: .328
Miguel Cabrera: .321
Stan Musial: .321
And Gwynn didn't get to play in Fenway and slap doubles off the Green Monster. (Gwynn hit .343 at home in his career, .334 on the road; Boggs, by comparison, hit .369 at Fenway in his career and .302 on the road. Maybe if Gwynn had played for Boston he would have hit .400.)
Another way to look at Gwynn's career average is he hit .338 during a time when the league average was .262 (via Baseball-Reference.com). Williams hit .344 in his career but the league average was .277. Sure, there's Ty Cobb -- .366 career versus a .273 league mark -- but if you need one base hit, one single, one dying quail to win a game, it's a short list of guys you want up there and Gwynn is on it. In situations classified as "late and close," Gwynn hit a mere .353.
Using slightly different numbers for league average, Lee Sinins calculates Gwynn has 73 points higher than his league average, trailing only Cobb (plus-94), Rogers Hornsby (plus-75) and Williams (plus-75).
How good was Gwynn? He hit .415 against Greg Maddux, .444 against John Smoltz, .469 against Doug Drabek. Those aren't small sample sizes as he faced all three at least 50 times. In fact, he faced Maddux more often than any other pitcher: 107 times. Never hit a home run off him, but drew 11 walks, hit eight doubles. Get this: Maddux never struckout Gwynn.