shikamarus a fodder ninja, hes the most overrated ninja in the world, hes important as a backup ninja and can fill the leading role, but hes not necessarily invaluable, every village probably has hundreds of ninja thinking of tactics, 10 people putting heads together is better than one, his brain power cant be more than thousands of ninja can it. who turned the tide of the 3rd ninja war, thats right minato. all that speed and power minato had made shikaku look useless, i mean i havent really seen anything from shikamaru except good timing and crafty tricks.
he could never be hokage like some of the fanboys are saying, a tactician hokage? the other ninja villages will be laughing, it was already going a bit far putting a healer as hokage, but a tactician? the other ninja villages will be laughing thinking "weve got thousands of tacticians" it doesnt matter if hes got the brain power of a supercomputer.
in a straight out battle shikamaru would be blown away by sheer speed, also could he protect the village from the kyuubi the way other hokages did? if shikamaru was hokage when naruto was born what would he have done against madara and the kyuubi? he would have been nuked.
his biggest achievement to date would be getting hidan tangled up in some paper bombs.