Well, I'd say that Nords, Redguards, and Orcs are the three strongest warriors in all of Tamriel- maybe other than immortals like Dremora perhaps. I'd say they're all about equally as strong just not in the exact same way. And Khajiit are probably the best at unarmored unarmored combat, though when people say "Warriors" they generally mean armor, and melee weapon.
If we're not focusing on things like training, and just raw, natural, untrained power, and focusing more on averages than exceptional individuals I'd compare the playable races of Tamriel like this.
Best mages: Bretons, Altmer.
Best warriors: Orcs, Redguards, Nords.
Most well rounded: Dumner. Consequently Dumner probably make the best Spellswords/Battlemages things like that as well.
Most socially influential: Imperials.
Most deadly in combat without weapons or armor: Khajiit.
Sneakiest: Bosmer/Khajiit.
Best Archers: Bosmer.