I have posted before that IMHO Genco was an overated consigliere. There is no evidence anywhere (other than anectodal evidence) that he was anything more than someone Vito considered to be almost a brother whose family took him in and allowed him to work in their grocery store. In the trilogy we only see him as a besotten wimp pining for an actress, a yes man opening the office door to the hapless landlord, and then acting as Vito's foil as the lady's rent gets negotiated down, and a delusional dying man who thought VIto could bargain for his life.

There is never any indication that he was a great wartime consigliere. In fact the only past mentions of war have to do with the novel, not the film, and that deals with Luca Brasi's incredible brutality, not Genco's tactics.

Moreover, I do not think Vito would name the olive oil company ater his most trusted advisor.

The good stuff we hear about Genco and the negative stuff we hear about Tom all comes from Sonny and Michael. Sonny the hot-head shouts "Pop had Genco and look what I've got." And then immediately apologizes. Michael cooly tells Tom "you're out" when he dismisses him before killing the heads of the other fmilies. Even this dismissal is sketchy because Tom sees through this ruse both in a deleted scene where he tells Michael he knows about the secret Rocco regime, and Vito announces he knew this would be something Tom was smart enough to figure out.

INstead of Tom being a bad consigliere who seems to be blamed for everything that goes wrong, I think we need to look at the shortcomings of Sonny and Michael who used him as a scapegoat when things went badly.
Tom was always looking for a peaceful way out, and had his advice been followed there never would have been a need for more violence after the hit on Vito and the retaliation on Tatt Jr. But SOnny and Michael wanted a war with more bloodshed and the consequences that followed.

It was Tom who Figured out the Tatts were in for a pieze of Sols action. It was Tom who found Fredo in New York and got him back after the Cuba episode. It was Tom who saw Michaell through the Senate debacle, and ended up demanding an apology from the committee. It was also Tom who calmly and methodically talked Pentangeli into committing suicide.

Despite the abuse his step brothers heaped on him, he remained loyal to the end, and even raised a son who became a priest.

He oversaw the money machine that was the original casino investents, and he was constantly being asked to leave the family to take legitimate jobs, which he always turned down.

All in all he was a brilliant consigliere, who never got the credit he deserved from Sonny, Michael or most of the people on these boards.

Vito summed it up best, and at the expense of his dead, beloved son. "I never thought you were a bad consigliere. I thought Santino was a bad Don, rest in peace."