The main character of each of these series has a special heart which has great power. The main character in each series has someone with great powers trying to help them & ward off everyone else.
The only real similarity between Magico and Tubame Syndrome is the basic plot, which is: the protagonist possesses a special heart capable of destroying the world and some people want to have it and use it, while others want to save him\her from harm. But thats where the similarities end. Tubame Syndrome is a so-so harem series, on the other hand Magico is a great action adventure series. If you find the basic plot interesting, you might want to check the other manga too.
Both of these manga revolve around a guy who has a special, supernatural, heart. In both cases, these supernatural hearts attract powerful superhuman and inhuman foes, as well as some powerful allies. The guys must fend off those who want their hearts, or their very lives will be forfeit.
The story of both of those series goes like this: A wimpy guy has a special heart and a harem. Nither of those manga is particularly good, but if you were fine with one of them, then you'll probably be fine with the other one as well.
Those two series are not exactly similar, but they do share a few themes. The main one would be a romance between an older alien girl and a highschool boy, the less important would be a ridiculous illness which the guy has. Qualitywise Onegai Teacher beats Tubame Syndrome 10:1, but even Onegai Teacher isn't a top of the line manga. Anyway if you read one and found the themes I mentioned earlier interesting you might want to check the other series (just keep in mind that Onegai Teacher is considerably better).