Raikage lost an arm and almost a leg to Sasuke who used incomplete Susano'o and he had just recently acquired his Mangekyou Sharingan techniques (inexperience). I don't think Raikage would be able to beat Itachi even with his speed. He was having a tough time taking on Sasuke and Sasuke was nowhere near Itachi's level. It was definitely looking bad for Sasuke during the fight but same can be said about the Raikage.
Itachi is said to be very fast (Kakashi's encounter with him). Kakashi's Sharingan couldn't track Itachi's hand signs or movement... Not saying Itachi is as fast as the Raikage, just saying he's fast too. I'll also mention that majority of Raikage's techniques are close combat. Itachi is a long range fighter who mainly focuses on genjutsus and diversions. For close range, he's got Susano'o with Yata's Mirror and Blade of Totsuka. Raikage is also not on the same intellectual level. Itachi has years of experience using MS and the normal sharingan. Raikage would not stand a chance.
i just like to point out some thing with you..
1. raikage lost his arm to sasuke's defense because sasuke can manipulate the amaterasu and put it to susanoo as a defense which itachi CANNOT do. lol did you see susanoo's rib broke from raikage's single attack? ouch! so much for the great susanoo.
2.we never saw raikage been affected by genjutsu, you cannot rely on itachi's genjutsu in this fight. sasuke didnt even use genjutsu to raikage for some reason.
3.being fast at waving hand signs is totally different frm moving fast dude.. itachi is NOWHERE NEAR raikage's SPEED! HE IS NEXT TO MINATO IN TERMS OF SPEED AS STATED IN THE MANGA.
4. well yeah sword of totsuka..as if susanoo is fast enough to hit raikage with that pityful sword. lol
5.oh yeah you also mentioned experience?? raikage is much older and A LEADER OF A VILLAGE.. sorry but itachi's battle experience is way fewer that raikages.
so much for an itachi fanboy. this one goes to raikage.