It's sad to me that there's not any specific performance I can point to to justify my love for this Jewish actor from Liverpool but I blame that on the kind of movies he ends up in (Elektra --ewww!) the company he keeps (Paul WS Anderson, director of 'classics' like Resident Evil is reportedly his best friend and they work together a lot) and the lack of diversity in his roles: filmmakers love him in villain mode which you can see from his gigs in Harry Potter (as Lucius Malfoy), Dragonheart (as Lord Felton) and The Patriot (as Col. Tavington) among others.
I personally don't care for him as Lucius Malfoy but I blame that on the silly blonde wig and the lack of depth to all the roles in that magical franchise. The point is: It's never Jason's fault! I can hate the hair but I can't hate Jason. It helps that he has a sense of humor and calls it "my Paris Hilton wig". Mr. Isaacs seems at peace with his sinister Hollywood typecasting niche saying in interviews
There is a streak of cruelty in me...
Now he doesn't always play a villain. Sometimes he's a priest, soldier, or the husband of a more famous actress. But more often than not those piercing pale eyes, that dark receding hairline, and his dangerously masculine vibe inspire evil thoughts... and thus, perhaps, evil roles. But whether he's in buttoned up or savage mode --or both (as he was in his dual role as Mr. Darling / Captain Hook in Peter Pan, 2003) --I'll take him.
[editors note: These photos are borrowed from two great Isaacs fansites: here and here]