The F-15X would be a far more cost effective fighter. With the current upgrades it still dominates any known opponent. The bottom line is, it's not stealthy and therefore it's not pretty anymore to the Perfumed Princes at Air Force Systems Command at Wright-Patt.
The F-35 has the stench of McNamara's ghost all over it. It will take at least two more generations of fighter development before the engineers achieve a one size fits all solution.