I agree with AKM Sama, Goku is 3-A or above in all his forms. Also, the wording for Base Goku and SSG Goku mentioning above is bad. The answer is, Base Goku is stronger than SSG Goku was, who was 3-A even back then. But as of RoF saga and above, Goku and Vegeta grew in power to the point where even their base forms are SSG level with each form still being stronger than the last as far as SSJ, SSJ2, SSJ3, SSG, SSB, SSB Kaioken x2-20, ect. It's similar to how later in ToP, SSB Goku and Vegeta became stronger than UI Sign was, but the current UI Sign and UIM are stronger yet.
Goku doesn't just get stronger from learning new transformations, he's always training to be stronger than yesterday, and often times the jumps are so great, that even his base forms and weaker transformations are stronger now then their strongest forms were. It's not like Base Form Goku is forever below Frieza saga SSJ just because he can still go SSJ. It's not like SSJ is forever below Cell saga SSJ2 just because they can still go SSJ2, and it's not like SSJ is forever below Buu Saga SSJ3. Goku constantly grows to where even Base Goku would solo all of Freiza saga, or SSJ would beat Super Perfect Cell, or SSJ2 would stomp Super Buu. Or heck, Super Goku is easily above all previously mentioned foes in his base form and always has from the beginning of Super. But Base Goku also happens to be universal due demonstrating BoG levels of power even now. His sparring match with Beerus disguised as Manoka was also a hint for that. As well as Base Goku being able to land a solid hit on Hit when SSB Vegeta was stomped. They both got a lot stronger now from then, but even back then, their base forms are easily universal.
Anyway Cabba has been Universal even in ToP saga. There was the fact that even Frost was Universal given he gave Base Goku trouble; when he is easily stronger than his RoF counterpart. And Goku possibly considered him stronger than 4th form Frieza in RoF though not as strong as Golden Frieza. Vegeta one-shotted Frost in SSJ form as he saw no need to toy around like Goku did in his SSJ form. And he actually did see potential in Cabba, as Vegeta upon getting Cabba to reach SSJ2 felt the need to use SSB despite not needing to use it against Magetta or Frost. Caulifa and Kale are also both comparable to Cabba. The Pride Troopers excluding the top three were all fodder that the saiyans literally did nothing but toy with and even Android 18 stomped them.