Dude was never a bad rapper. In fact he had a lot of gems on Power of the Dollar. He changed his style up for sure, and started conciously trying to make more catchy records. But he was never wack. Definitely not on the level of a lot of the people he was in the same league as in terms of sales numbers, and he was often compared in mainstream media to cats that were well above him (like Jay and Nas, etc.) but 50 was always a solid rapper. He was just very one-dimensional and his gimmick got old eventually.
Power of the Dollar, GRODT, and The Massacre were all solid albums.