I completely agree with what Theodin said. Having the ability to beat one top team does not make you the best team. That's not how competitive player works, it isn't so linear. G2 might simply have a setup which SK are poor at countering whilst other teams can to a certain extent. Before Malmo, the last best of three that G2 played was against EnvyUs which they lost!
And SK has actually had more recent success in terms of tournament wins than G2 has. Let's not forget that, before the major, SK won 5 out of the last six events that they had attended. Yes some of them were tier two events but that just shows that SK's achievements outnumber those of G2 in all respects. You can't say that SK are top because of past achievements because the rankings work in a degrading fashion meaning that past results become less relevant the more time that passes. Their old achievements won't count for much in terms of their rankings so they'll be reliant on more recent successes to maintain their ranking.