Igor was already in decline by the time Shogun was rising up around 2004 and 2005.
Igor kept hurting his hands which was also his main weapon. Dude hit so hard the impact shattered his hands over and over.
Igor had also been fighting since 1995 and he had like 80 MMA fights and 60 kickboxing fights.
Shogun was in his young 20s as Igor was slowing down.
They are essentially from two different eras. Their primes would have never coincided, however, it still could have possibly been a decent or entertaining match around 2003 or '04.