These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Hilarious in Hindsight: Half the pros. Many of them took steroids (Barry Bonds and Sammy Sosa), and many have their own specific reasons (Ricky Williams chose drugs over Football).
Memetic Badass: Pablo Sanchez, full stop. For just about every single player, he's the first pick. His incredibly high Game Breaker level stats combined with being a Bilingual Bonus made him the single most popular character in the series, and survived when the games went 3D.
If you really want to get specific on how the Sequelitis started, the company who had started the series, Humongous Entertainment, went bankrupt after a failed experiment. All the rights were sold to Atari, Inc. after 2002. They made all of the 3D titles, and have caused decline in quality ever since.
They Just Didn't Care: The later games until Sandlot Sluggers, with robotic announcing, bad controls and graphics, and barely any background sound whatsoever.
Vindicated by History: The early Atari titles weren't well-recieved when they were initially released. After the 2007 games rolled around, though, most fans went back to those and realized that they were actually faithful to the original games in comparison.
Viewer Gender Confusion: You can make this happen yourself with the custom players in most games, if you give them the opposite voice of their physical appearance.
Certain installments of the series provide examples of:
Accidental Innuendo: In Soccer 2004, one of the fields is called Fappy's Farm (or just Fappy Farm, which arguably sounds even worse).
Contested Sequel: 'Backyard Baseball 2001 and Backyard Soccer: MLS Edition. People debate whether the addition of pros, who make up half the playable characters in Baseball 2001, is good or bad.
8.8: IGN's review of Backyard Basketball on the PS2, giving it a 6.5 (the exact same score of its predecessor) despite fan acclaim.
"Funny Aneurysm" Moment: Michael Vick's in-game nickname is "Mr. Electric". Guess something he's done to dogs.
Hilarious in Hindsight: In Baseball, Stephanie Morgan, when pitching, says she models her pitches off Randy Johnson, who actually became playable in Baseball 2001.
Porting Disaster: Football on the GBA. Apart from being painfully slow, we also get very low difficulty and annoying controls.
Scrappy Mechanic: Running, for the outfielders in Baseball, although fielding can account for this as well.
Surprisingly Improved Sequel: Basketball on the PS2, as well as Basketball 2004 on the PC, gained the NBA license and ironed out a lot of the bugs the original had. Of course, this didn't stop IGN's aforementioned 8.8.
They Wasted a Perfectly Good Plot: They could have done something with the pros when they first appeared other than make them the poster boys for the series.