they were almost of the same age. Even then, Shishui was feared by ninjas from other villages. I don't think they knew Itachi as such.
And Shishui is stronger doesn't mean that Itachi is a fodder.. you have to know that.
Not almost the same age. Shisui was a young adult jonin who had the priviledge of having his own team. That and his father Kagami was the same age as Hiruzen. He was anywhere from 5-9 years older than Itachi. That and since he was more public and went on missions with his team, regardless of whether his abilities were better or not, he'd be more well-known than Itachi who worked in the shadows as an Anbu. Therefore, Shisui being more well-known isn't an indicator of him being stronger than Itachi, and even in the anime episodes, a 13 yr old Itachi has better feats than an adult Shisui...and in the manga Itachi still has better feats while Shisui is featless.
ot: Danzo stole Shisui's eye after he let down his guard entirely and then summoned backup. Shisui was obviously stronger than Danzo, and if he had just left after getting Danzo caught in that 3-tomoe genjutsu, he would have been fine. Does Itachi ever let down his guard or is he the type to do so? No. When Oro attempted to attack him, he caught him in a 3-tomoe genjutsu, made sure to watch him, cut off his hand, and left. That was when Itachi was 14. If Danzo attempted to take Itachi's eye, back when he was in the village as a 13 yr old, Itachi wouldn't cut off his hand or hurt him physically (that would cause more tension if an Uchiha hurt a village elder), but just catch him a 3-tomoe genjutsu like he did with Oro and leave. So, no it would end up differently and Itachi would be fine.