Jerry O'Connell did nice work in MY SECRET IDENTITY and SLIDERS, but he's never played any significant roles outside of that. Sure, he's been in significant projects, but he didn't bring anything that he and only he could offer to his characters in SCREAM, MISSION TO MARS, TOMCATS or KANGAROO JACK.
After that dark period, however, Jerry seemed to seriously rethink his life and work. He did some nice stuff as CROSSING JORDAN's Woody Hoyt, but he was supporting Jill Hennessy and he was by necessity low-key. His Tom Cruise impersonation was delightful. Since then, he's done decent but undistinguished work in various short-lived TV shows and movies -- again, low-key stuff. A lot of this seems deliberate -- just looking for steady work where he can do a focused, thoughtful job, not worrying about finding a career defining role because he's earned enough to take care of his family. The only role Jerry seemed to hunger for to the point where he actively campaigned for it -- he wanted to play Quinn Mallory again in 2013.
John Rhys-Davies is a great actor and performer, but sometimes he settles for being a performer and playing himself. John's characters are often arrogant, lovably pompous, bombastic teachers. Because his roles are so similar, it's hard to pick one out as the best. Also, John has usually been a supporting character. I would say that my favourite work from him is in STAR TREK VOYAGER where he played Leonardo da Vinci in an unusually measured, thoughtful performance across two episodes and was different from his usual template.
Cleavant was hilarious in the sadly short-lived David Kelley series THE WEDDING BELLS.
Sabrina was in SPORTS NIGHT, which I've never seen, but Sabrina's stage-oriented acting and Aaron Sorkin's scripting seem a good match at least in theory. She's very good in UNIVERSAL SIGNS (a silent movie) and in DOPAMINE as a troubled teacher. She's also in THE PRETTY ONE with Zoe Kazan, but I have no memory of who she played.