I think the thread title is somewhat self-explanatory, though obviously the concept of being underrated is subjective and by mere mention here, these players are not really 'forgotten'. But I think you get what I'm going for. These are a players who would often elict an "oh yeah" reaction when brought up among top baseball hitters in history, as opposed to being listed or remembered outright.
Dolph Camili - In an era where walks were seen as unequal to hits and strikeouts as the ultimate sin, Camili's game had to infuriate purists who believe in hitting and making contact, not walking and striking out. From 1934 to 1941 he had a line of .286/.396/515/.911 and averaged 25 HRs, with two 1.000+ .OPS seasons. That's damn impressive, strikeouts be damned.
Sid Gordon - Sid Gordon played his first full MLB season for the New York Giants in 1943 at age 25. He spent 1944 and 1945 serving his country in the United States Coast Guard during World War II. Now 28 in 1946, Gordon put up a .290./386./481/.867 line from 1946-1954, up until his age 36 season. For his work he received anti-Semitism, a few token MVP votes, and just two All-Star appearances. He wasn't even an All-Star in his .960 OPS season of 1950, while Dick Sisler and Johnny Wyrostek were.
Cecil Cooper - Being only 23 years old, Cecil played before my time. I knew he was a former player but knew him simply as the Astros manager. I was pretty surprised to see what a good hitter he was, averaging an .851 OPS from 75-83 with a few Gold Gloves to his credit as well.
Rusty Greer - The man who inspired me to create this thread. He randomly popped into my head earlier and I decided to look at his numbers. Whoa. He only had 7 healthy seasons, 9 in total, but in those 7 seasons had a line of .307/.392/.486, good for an .878 OPS.
Tim Salmon - From 1993 to 2000, Salmon had a .928 OPS with 228 HR's. But he eclipsed the 100 RBI mark 'only' two times, and while he was Mr. Angel, he was often overlooked in favor of teammates Garet Anderson, Troy Glaus, and Mo Vaughn's RBI totals and Jim Edmonds similar game and hot dog catches. He never appeared in a single All-Star game and has only a 1993 Rookie of the Year and a 1995 Silver Slugger award to his name.
Richie Sexson - Nobody ever talks about 'Big Sexy', perhaps in part because he played in the 'unremarkable' markets (no offense intended) of Cleveland/Arizona/Milwaukee/Seattle during his career before finishing with a whimper in New York with the Yankees in 2008 at 'only' age 33. But before heading to Safeco field in 2005, Sexson had a career .877 OPS with 200 home runs by age 29. He had his flaws, but possessed a respectable batting average and obviously prodigious power. The HR's were still there in 05/06 with Seattle as he hit 39 and 34 respectively, but he cratered in 2007 and was out of the league before the end of 2008.
Carlos Delgado - It feels kind of silly to say a guy who had 477 career HR's and just retired 4 years ago is underrated, but I really think people tend to forget just what a dominant hitter Delgado was. A career .929 OPS with two ridiculously stat sheet filling seasons in 2000 and 2003 with a 1.000+ OPS
Magglio Ordonez - Daddy Mags always seemed to fly under the radar, but man could he rake. A career .309 hitter with over 2000 career hits, Ordonez's 2007 season sticks out with 54 doubles, .363 batting average, and a 1.000+ OPS. Jose Canseco has accused him of PED use, but Jose Canseco says a lot of things.
J.D. Drew - He never could live up the insane hype his 1998 rookie season generated, but for a guy reviled by multiple fanbases, he managed a damn good career while constantly battling injuries. A career .873 OPS with two seasons of a 1.000+ OPS and a near .400 OBP from 1998-2009. Probably deserves a rose or two thrown his way instead of the batteries.
Feel free to provide feedback or add your own hitters!