That's because she is. She's a more dynamic character then Lightning. She doesn't complain the entire time like Lightning. She the definition of actual strength. Not Lightning. She's actually likable from the get-go. She's not bland, one dimensional and isn't monotone. She actually has personality.
If anything BbS is extremely consistent with its story and the characters don't say dumb things like:
Main villain: "Kill me so Cocoon can fall"
Lightning: "No. We will defeat you and do exactly what you just asked us to do."
*Cocoon Falls*
Like really? BbS's plot is miles better then XIII.
Does lightning complain all the time ??? At one point did you stop playing the game ? the hanging edge ? Do you realise she helped hope and snow reconcile ? She thought it was important for him to meet his father and recover from his trauma and see where he can go.
She teamed up with fang and forgave her even though she knew fang was the reason Serah is a crystal.She even helped fang fight her Eidolon and did the same with hope."You are not in this ordeal alone , you know" She said that.
In XIII-2 she put everything past her, even her sister for the sake of the world."One thing at a time serah" was her reply when Serah asked if they would unite.
She goes from angry , defeated into calm and passionate and then into determined yet unsure of her fate. She slips into depression in XIII-2 but regains her hope at the end(DLC)
I provided great details about lightning and analyzed her character as quickly as I can.You , however, simply label her as bland, emo , and less dynamic than Aqua without giving any concrete or valid points.
Like I said Aqua is very likeable but extremely flat.She is caring about her friends and that's fine but could you point any other trait ? There are none.