Are we talking in terms of power, or overall quality as a series?
Power-wise, Super has Universe busters, GT doesn't and I don't believe Multiverse has any feats close to Multi-Galaxy busting since I last read it at least, so Super >>>>> GT >> Multiverse.
Quality-wise, GT at least bothered to develop its cast and give the series a proper conclusion. Super is just a cashgrab that is being stretched out far longer than its logical conclusion as an intermediary part in the timeline whilst making each of its characters a disrespectful caricature of their former selves and all the new characters being either bland or terrible. Multiverse is just generic fanfiction that uses the idea in a far less creative way than even Super did due to purely focusing on previously established characters and save for perhaps Vegetto, none of them get development. They also try too hard with the plot twists to the point it feels as nonsensical as Bleach. If I wanted decent alternate timeline stories, I'd rewatch a select few episodes of Futurama or Justice League.
GT >> Super ~ Multiverse in terms of quality.