If you're wondering how these players' careers are shaping up, their stats so far are pasted below. Some of them had slow starts to their careers, but they're all getting into their primes now as we enter season 5.
Sorted by career HR leaders through 4 seasons:
Ted Williams G:627 AB:2385 R:606 H:838 2B:163 3B:17 HR:144 RBI:595 BB:498 SO:272 HBP:16 SB:0 CS:0 AVG:.351 OBP:.466 SLG:.615 OPS:1.081 LSTRK:23
Mike Schmidt G:505 AB:1928 R:359 H:477 2B:97 3B:5 HR:128 RBI:384 BB:300 SO:517 HBP:10 SB:14 CS:3 AVG:.247 OBP:.352 SLG:.502 OPS:.854 LSTRK:12
Eddie Mathews G:647 AB:2409 R:352 H:598 2B:92 3B:14 HR:122 RBI:361 BB:355 SO:493 HBP:10 SB:1 CS:1 AVG:.248 OBP:.347 SLG:.450 OPS:.797 LSTRK:11
Frank Robinson G:648 AB:2578 R:422 H:699 2B:115 3B:18 HR:111 RBI:416 BB:247 SO:452 HBP:42 SB:13 CS:12 AVG:.271 OBP:.345 SLG:.459 OPS:.804 LSTRK:18
Jimmie Foxx G:549 AB:1885 R:343 H:593 2B:96 3B:17 HR:104 RBI:363 BB:277 SO:316 HBP:8 SB:1 CS:1 AVG:.315 OBP:.405 SLG:.549 OPS:.954 LSTRK:16
Willie Mays G: 525 AB:1997 R:387 H:606 2B:90 3B:30 HR:100 RBI:342 BB:226 SO:274 HBP:15 SB:22 CS:13 AVG:.303 OBP:.378 SLG:.529 OPS:.907 LSTRK:18
Eddie Murray G:639 AB:2320 R:268 H:625 2B:114 3B:2 HR:96 RBI:337 BB:257 SO:361 HBP:9 SB:0 CS:3 AVG:.269 OBP:.345 SLG:.444 OPS:.789 LSTRK:11
Frank Thomas G:593 AB:2083 R:331 H:603 2B:105 3B:4 HR:94 RBI:422 BB:351 SO:340 HBP:16 SB:0 CS:1 AVG:.289 OBP:.396 SLG:.479 OPS:.875 LSTRK:13
Mark McGwire G:452 AB:1574 R:236 H:402 2B:54 3B:6 HR:92 RBI:298 BB:226 SO:322 HBP:4 SB:0 CS:0 AVG:.255 OBP:.350 SLG:.473 OPS:.823 LSTRK:15
Hank Aaron G:635 AB:2524 R:381 H:768 2B:141 3B:22 HR:91 RBI:402 BB:166 SO:255 HBP:19 SB:2 CS:4 AVG:.304 OBP:.352 SLG:.486 OPS:.838 LSTRK:18
Ernie Banks G: 486 AB:1831 R:275 H:503 2B:88 3B:10 HR:88 RBI:317 BB:169 SO:298 HBP:9 SB:6 CS:1 AVG:.275 OBP:.337 SLG:.478 OPS:815 LSTRK:13
Reggie Jackson G:546 AB:1864 R:289 H:432 2B:78 3B:13 HR:80 RBI:259 BB:232 SO:535 HBP:17 SB:32 CS:24 AVG:.232 OBP:.322 SLG:.416 OPS:.738 LSTRK:11
Ken Griffey Jr. G:604 AB:2352 R:371 H:673 2B:131 3B:14 HR:75 RBI:346 BB:191 SO:383 HBP:12 SB:23 CS:10 AVG:.286 OBP:.343 SLG:.449 OPS:.792 LSTRK:15
Mickey Mantle G:614 AB:2031 R:354 H:577 2B:106 3B:15 HR:71 RBI:300 BB:256 SO:451 HBP:11 SB:4 CS:3 AVG:.284 OBP:.367 SLG:.456 OPS:.823 LSTRK:18
Barry Bonds G:554 AB:2038 R:313 H:505 2B:99 3B:18 HR:68 RBI:329 BB:225 SO:367 HBP:8 SB:83 CS:42 AVG:.248 OBP:.325 SLG:.414 OPS:739 LSTRK:14
Manny Ramirez G:484 AB:1781 R:277 H:477 2B:92 3B:6 HR:68 RBI:318 BB:212 SO:385 HBP:14 SB:0 CS:1 AVG:.268 OBP:.350 SLG:.441 OPS:.791 LSTRK:8
Mel Ott G: 429 AB:1270 R:227 H:372 2B:64 3B:3 HR:61 RBI:224 BB:182 SO:151 HBP:5 SB:0 CS:1 AVG:.293 OBP:.384 SLG:.492 OPS:.876 LSTRK:12
Alex Rodriguez G:453 AB:1461 R:206 H:404 2B:76 3B:10 HR:48 RBI:221 BB:97 SO:280 HBP:12 SB:15 CS:9 AVG:.276 OBP:.327 SLG:.441 OPS:.768 LSTRK:10
Babe Ruth G: 253 AB:768 R:112 H:222 2B:66 3B:11 HR:38 RBI:158 BB:93 SO:192 HBP:9 SB:0 CS:1 AVG:.289 OBP:.372 SLG:.552 OPS:.924 LSTRK:8
Willie McCovey G:376 AB:629 R:87 H:168 2B:25 3B:3 HR:27 RBI:83 BB:80 SO:112 HBP:3 SB:0 CS:1 AVG:.267 OBP:.353 SLG:.445 OPS:.798 LSTRK:12
Rafael Palmeiro G:471 AB:1521 R:190 H:414 2B:76 3B:5 HR:25 RBI:220 BB:118 SO:97 HBP:4 SB:3 CS:1 AVG:.272 OBP:.326 SLG:.378 OPS:.704 LSTRK:13
Jim Thome G:304 AB:809 R:107 H:200 2B:37 3B:5 HR:25 RBI:127 BB:70 SO:225 HBP:8 SB:0 CS:0 AVG:.247 OBP:.313 SLG:.398 OPS:.711 LSTRK:20
Gary Sheffield G:388 AB:1045 R:142 H:268 2B:57 3B:5 HR:15 RBI:109 BB:79 SO:90 HBP:10 SB:32 CS:18 AVG:.256 OBP:.315 SLG:.364 OPS:.679 LSTRK:12
Sammy Sosa G:253 AB:275 R:62 H:75 2B:5 3B:1 HR:8 RBI:32 BB:13 SO:62 HBP:7 SB:26 CS:14 AVG:.272 OBP:.322 SLG:.385 OPS:.707 LSTRK:5