Tiger beats any middleweight that comes to him and slugs. Thats basically what Jake's repetoire was, and Tiger would have won a solid decision over 15 rounds.
Jake could box when the situation called for it, and he could screw up an adversary with his switch hitting. I lean towards him, but with no great conviction.
Hagler wouldn't even slug with guys like Briscoe and Sibson. Ketchel was outslugged and KO'd once by Billy Papke, and reportedly held to standstills by Langford and Frank Klaus in slugging matches.
The only way to beat the middleweight Tiger was to box, box, box, jab, jab, jab...boxers were his weakness...and only good boxers.
Hagler would box Tiger not brawl with and Ketchel would lose. Not sure about Greb there is no footage of him. Interesting to see how Tiger would do against Walker and Valdez.
I think that fight comes down to how well Greb can box and how long into a fight he can keep it up. He looks pretty quick on his toes in the video of him sparring, so it's possible he could give Tiger the same kind of troubles Griffith did. At the same time though, from reports it seems that some of the very few fighters who did beat or trouble Greb (ie: Mike O'Dowd, Tunney) did so by stepping into him and working his body - so who knows? I would favor him over both of them.