Opinions are like that, unfortunately.
It's the same a calling a game "shit" or "garbage". There seems no middle ground for some people. It's beyond annoying, especially (for me) when you see a game that you consider a masterpiece and a step towards the right direction for the genre, such as Ni no Kuni being called "garbage". You might not like it, but that doesn't make it freaking "garbage". Same with COD, which I don't care for. It might not be perfect (or even close to it), but garbage it is not.
As for Bomba, I've noticed that it's used
a. for fun from some members
b. as retaliation from others (you called my favourite ninty game a bomba, I'll call your ps3 exclusive bomba, cuz it serves you right, you fanboy)
c. out of malice. I hate Sony, so I'll call GT6 a bomba because it sold less than the previous one, that it the best selling ps3 exclusive
d. because it did lower than decent numbers (based on expectations)
e. because it did absolutely terrible and the studio might even go bankrupt (which is sad and not something to laugh about, people).
Flop is even more complicated because it is actually based on expectations. I think the (movie) "Three Musketeers" was a bomba and not a flop, because it did horrendously badly.
People could use the term "underperformed", but they seem to think that the more absolute they are in their statements, the stronger the statements are.
