And I generally prefer longer-running shows, but I can say with certainty that I would have liked Code Geass far more if it were at least several episodes shorter.
In Japan Gundam Seed Destiny is the 4th best selling tv anime of the past 20 years. When it aired Gundam Seed, and Gundam Seed Destiny got ratings that Gundam hadnt seen in 15 years since Zeta Gundam and ZZ Gundam.
It also kind of gave a huge kick in the pants and revival to the whole franchise. The series kept doing worse and seeing declining ratings, model kit sales, and general popularity. SEED reinvigorated the entire franchise, and ushered in a huge new era of fans into Gundam as well.