it has to be the rb26dett, besides the obvious point being that it comes from the gtr( nissans hero car), it's the easiest engine to get good power out of without needing to open the engine up, getting a new ecu, or doing much or any fabrication.
Also another plus it has over engines such as the vg30dett,vq30/25de/tt range and the vh45 ect lies in the fact that it's a straight six, where as you'd think this would be a disavantage( in a properly engineered racing engine it would be) but in comparison to nissans v engines the straight sixes have a lot more internal strength, along with the fact that there a lot more compact.
it's also one of the larger nissan straight sixes yet it's still over square alowing it to rev damn hard, while this does nothing for torque levels it certainly more then evens out in total power production.
yes it is rated very highly by most people but for good reason, the only reason it seems so over rated is because other engines of similar stature are extremley under rated, such as the 1jzgte