Melina got MNM over, and got Nitro over during his solo run. You can go on about their ring work all you want, but c'mon, neither Nitro nor Mercury would've gotten any real heat without her. Hence her getting all the promo time during that run (Nitro and Mercury got what, two or three promos in two years?), and hence her being the one who ultimately remained in the spotlight when using the Hollywood gimmick.
Melina's advantage over Maryse is that she can draw heat. Maryse's character is snobbish and arrogant, but she's too laid back to get people to react (cat calls aside). Melina as a manager was able to provoke genuine dislike through the screaming, the bitching, the in-ring interference and all the OTT heelish stuff she did. Similar to Stephanie McMahon, but with less impactful storylines and angles. People just seem unwilling to admit to it.
I think she could bring a spark to Gabriel, Slater and the Corre in general. I'm not saying they're bad, but there's something bland there. Melina is nothing if not animated.