People like different things.
The reason Ulduar is such an important raid and praised as godly is because WOTLK was the time when wow really became popular and raiding became less elitist = many more people experienced it.
Ulduar was my first ever raid done as current content and it will always have a special place in my heart. But yes, I think I enjoyed ICC more. On some level, nothing will ever beat Ulduar though.