In order to save the twenty bucks, you have to purchase either ALL games or ALL accessories.  As long as you plan on maxing out your controller stash on day one, or buying a couple of launch day stinkers, you'll be fine.
The following games will be out on launch day: 
  4X4 EVO 2 
  AirForce Delta Storm 
  Cel Damage 
  Dark Summit 
  Dead or Alive 3 
  Fuzion Frenzy 
  Halo 
  Mad Dash Racing 
  Madden NFL 2002 
  NASCAR Heat 2002 
  NASCAR Thunder 2002 
  NFL Fever 2002 
  NHL Hitz 20-02 
  Oddworld: Munch's Oddysee 
  Project Gotham Racing 
  Shrek 
  Test Drive Off Road - Wide Open 
  Tony Hawk's Pro Skater 2x  
  TransWorld Surf 
Halo's about the most impressive.  Tony Hawk is probably good as well.  I've heard disappointing things about Oddworld.  I played Cel Damage: imagine Twisted Metal mixed with Whacky Races.  Dark Summit will be eclipsed by SSX Tricky, when it comes out.  I don't play sports games and I won't touch anything with the word "Shrek" on it.  Not sure about the rest.