I think Ted could have had a longer run if not for a few things.
The first is a common rookie mistake. He spread himself too thin.
He was taking on way too much work and that backfires
You saturate the radio with your sound and people get tired of it or it gets predictable
Ted brought in a slew of apprentices to help him even out his work load but that didn't stop the burnout
Ted got lazy and started leaning on ripping off old records instead of writing new music.
Teddy's Jam 2 is an example of this. It sound like a overdone homage to Atomic Dog rather then the refreshing groove of the first Teddy's Jam
The rip off of DeBarge's Time Will Reveal for Blackstreet's Jesus Is Real was blatant, lazy, and shameful even though it got a ton of radio play.
The work he did on Michael Jackson's Dangerous was his creative peak (in part due to MJ's mentoring and co-production) and he's not come close that level of innovation since.
That said, Teddy Riley saved R&B from an awful place, changed the face of music production forever and left a long trail of classics in his wake.
He continued to influence R&B and hip-hop after his heyday through his protegees, Timbaland and The Neptunes.
For that, Teddy gets 10/10. He is one of the most important producers in the modern era of music, period.