Aside from everyone's favoritism or subjections...

...being marketable is the main issue here.

Rihanna was simply....more marketable than Teairra Mari.

In my opinion, Teairra Mari has more talent...more personality...& overall...more of a presence than Rihanna. Sadly, her musical content was lacking --- although the production quality could have easily rivaled the likes of Timbaland. However, you have to attribute all of that to the powers that presided over both of them.

In my opinion, Rihanna is a puppet. She's a horrible performer [i.e. '07 MTV Movie Awards], her voice is sub-par, & her stage presence [interviews] really makes her come off as quite boring...& extremely aloof.

Unless she starts taking control over her own material & crafts what little talent she has into a respectable mold...I don't expect Rihanna to have longevity in the music industry.

Rihanna was the easiest to transform into a marketable crossover artist --- she appeals to all demographics. It was no mistake that Teairra Mari's content was one-sighted...b/c the record company intended for it to be that way. She didn't write any of those songs or produce a single track --- her image was crafted [by the record company] around her personality.

Unfortunately, her personality was not crossover-ready.