I don't know if this fits under "underappreciated" (probably not) but i played the **** out of NASCAR Thunder 2003
This game. This freaking game.
Picture me, a boy that didn't knew any english, didn't had access to internet or any international tv channel. I had absolutely no idea what i was playing.
But the numbers, the colors, the tracks, the oval racing... THE DAMAGE MODEL AND THE PITSTOP! I won't ever forget them. When the channel SPEED came to my country i could finally see what's a real NASCAR racing and immediately i remembered all those cars from this game.
I could finally understand those names: Jeff Gordon, Elliott Sadler, Tony Stewart, Greg Biffle, Todd Bodine, Jeff Burton, Dale Jarrett, Dale Earnhardt Jr, Kurt Busch, Dale Earnhardt Sr, Bill Elliott, Kevin Harvick, Jimmie Johnson, Matt Kenseth, Mark Martin, Bobby Labonte, Terry Labonte, Ryan Newman...
I'm not ashamed to say: NASCAR games teached me everything about, well, NASCAR. After this game, i bought every nascar game for PS2. This is a series that i happily played for hours and hours. Pretty sad how we really didn't had any "good" NASCAR games on PS3. I played Eutechnyx's 2010 and 2014 but... they're not even close to be funny as EA's (sadly). Haven't got the chance to play the most recent ones.