"Mass Effect" is a euphamism for "The second best thing ever invented". The first being, of course, Mass Effect itself. If a person loves something very much, they may say it is Mass Effect. If they say this they mean that thing is the best thing ever invented since Mass Effect itself.
Guy: Oh, man, I really love Carrots."
Girl: Really? How would you describe your love for carrots?
Guy: I'd say Carrots were Mass Effect.
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