Who was bigger?

From what I can tell, Mapusaurus is slightly larger than Giganotosaurus, basing off of a pubic shaft alone. The shaft is about 1.22% larger, leading to a 13.2 meter, 6-7 ton estimate for Mapusaurus. Carcharodontosaurus alone is approximately 11-12.2 meters at their maximum.

Giganotosaurus is about 12 to 14 meters and 7 yo 9 tons. So it is heavier then mapu but is the same length.

Giganotosaurus, just as long as the other 2 but more Robust which equals a heavier animal.

weights for the animals

mapusaurus 6-7 tons 

Carcharadontosaurus 6-7.5 tons

Giganotosaurus 7-8.5 tons

They're so close there's no definite answer. Ask six different people, you'll probably have three different answers for six different reasons. I'm neutral on this topic. 

SCIENCEDEGREE605 - What a very interesting question! Unfortunately, as many have already pointed out, it also happens to be a difficult one. More or less, one can surmise from the remains paleontologists have unearthed that the three animals in which you have expressed interest seem to have grown to similar sizes. With that being said, the amount of data currently available simply is not extensive enough to make a solid case for any one of the three being larger than the others. I know this is not exactly the answer you desired, however, look at the situation in this light: your own hypotheses concerning which of these three animals is largest can not be refuted. If you say Carcharodontosaurus is the largest, there is no definitive way (as of yet) for anyone to state that you are wrong. With this as the case, speculate away! I certainly hope this helps you to some extent. Regardless, thank you so much for asking this very compelling question! :)

Godzilla is the biggest !