IMO, Romo should probably be a Hall of Famer. He'll never get in because his Cowboys teams never won jack, but you can argue that he's one of the top 5 QBs of his era. PFM, Rodgers, Drew Brees, Brady, and then I think he stands up to anyone else you care to name after that. Not in terms of stats or Ws, but in terms of pure individual play. Phil Rivers is right there with him too IMO, but he's not getting in either.
Both Romo and Rivers were stuck carrying really dodgy rosters from about 2009-2013, so they'll always be remembered as "stat stuffers" rather than champions because their teams wouldn't allow them to go any farther than 8-8. Eli and Ben are HOF locks based on their Super Bowls, but if you watched them play, Romo and Rivers were always better than them and for Manning especially it wasn't really close.