Well if you don't beat Red at all you can't get any of the 3 Kanto starters(Bulbasaur, Charmander and Squirtle). And you can't get the Red Orb(Soul Silver) or the Blue Orb(Heart Gold), which summon Groudon(Soul Silver) or Kyogre(Heart Gold) at the Embedded Tower on Route 47. And if you don't have Groudon and Kyogre with you when you meet Prof. Oak at his lab, you can't get the Jade Orb from him, which summons Rayquaza. Hope I helped!
Source: Experience