GOAT in baseball is so tough. Bonds is it, but he's disqualified, IMO. Then Ruth is it, but it's tough to say that a guy who played in the 20's without anybody but white Americans is the GOAT. Then Ted Williams is it, especially when you consider that he lost 3 of what would have surely been his best years. But you also have Mays, who combined great (if not quite as great) offense with far better defense than anybody else in the discussion. Hank Aaron always gets overlooked to some degree in the discussion, and he's not the GOAT, but he at least deserves some notice for his longevity and sustained excellence.
And then you have all the pitchers.
It's hard for me to say that Trout looks like he will be the best ever. His instant jump to all-time great at age 20 was incredible, and his consistency has been remarkable. But will he have the peak that some others did? And how long will he sustain it? It's hard to say. But my ranking would probably go something like this:
1. Willie Mays
2. Ted Williams
3. Babe Ruth
4. Ty Cobb
5. Barry Bonds (without roids)
with Aaron, Gehrig, Hornsby, and Musial just missing.
If Trout continues this level through age 29-30 and then continues playing good baseball for another 5 years or so after that, he will begin to enter that top 5 territory.