Here are the 4 most comparable players to Trout through age 26, per Baseball-Reference:
(1) Frank Robinson; (2) Ken Griffey Jr; (3) Mickey Mantle; (4) Hank Aaron
...and that's before this season, which may be his best.
At age 27, he has more career WAR than Ernie Banks, Tony Gwynn, Eddie Murray, Ryne Sandberg, Duke Snider, Craig Biggio, Andre Dawson, Roberto Alomar, and more HOFers had in their entire careers. Before the season is over, he'll probably pass Derek Jeter, Barry Larkin, Frank Thomas, Reggie Jackson and Johnny Bench.
He is the definition of "transcendent" (though I guess it depends on what you mean by the word). The dude is a fucking unicorn.