I said some unflattering things about Hal Wallis's post-Warner-Brothers producing career in an earlier post, so for an alternative (and probably fairer) assessment, check out this article by Ed Sikov about Wallis and his business partner, Joe Hazen. He makes good points, even if he is writing at a site that was financed by Joe Hazen's foundation.
I still have my problems with most of Wallis's Paramount filmss, most of which -- even the good ones -- seem kind of stodgy compared to what he was doing at Warners. (He always liked making films out of stage plays, but his Paramount adaptations actually do feel like filmed stage plays, even to the point of hiring stage directors who were deadly dull on film, like Peter Glenville.) But it's true that he did produce a lot of entertaining movies, and, as Sikov notes, his arrangement at Paramount -- as a quasi-independent producer working at a major studio -- showed his grasp of how movie production would work in the post-studio-system era.
Also, in the DVD booklet for The Furies, an early Wallis production at Paramount, Anthony Mann is quoted as saying very good things about Wallis as a producer.