I think the problem is that both ME1 and DA1 are fundamentally different games from those that came after. I think at the time I used to think that ME1 and DA1 were built to a PC game standards, and ME2+ and DA2+ were built for consoles.
Most companies started doing the same around that time. It's easier to port a game designed for a controller to PC than a game designed for keyboard and mouse to consoles.
Bioware was always trying to reinvent the wheel. They never wanted to make the same game twice. It was both their strength and their weakness. Every time they released a sequel, it felt different than the previous game (except maybe ME3).
In my opinion, ME2 was the last unambiguously good game Bioware released. They made a few good games after that, but every game starting from DA2 also had major issues.
