Let me start this one by saying
I am not a gigantic halo fanboy. The first one was good, the subsequent ones... adequate. But it's the mindset that each installment represents that I want to talk about here.
Halo 1 was a solid game from any standpoint. The gameplay was pretty well paced, the art was pretty for the time and console, and the story was intriguing. Halo 1 was a good example of a game made by people who wanted to make the game they wanted to play. Each level was different enough from the last and introduced a gameplay mechanic that seemed like bungie wanted to explore some different aspects of level design. Bungie was a well established developer before they made Halo 1, but I think they had fun making it, which is the whole point of making games, isn't it?
Halo 2 was, in my opinion, pretty fucken horrible. The engine had some serious flaws, the renderer couldn't make up its mind for the art style, the gameplay was, well, fast and hard and kind of fun, but overall forgettable, and I don't know if it was just me or the storyline was actually just breifly glossed over. Halo 2 felt like the kind of game that a studio that has just made it big and needs to capitalise on their success by pumping out a sequel would make.
Halo 3 was a very deliberate game. The art direction was strictly adhered to, the engine was refined to a fine machine and the storyline was explored fully. This is what bigtime professional game develolment studios make. Admittedly, there was no real exploration of new exciting mechanics or strange development quirks, which is the way of big game companies, they pointedly amd tenaciously stay with the tried and true in order to satisfy fans and maximize profit. But that doesn't have to ne a bad thing, I'm looking at you, EA.
You can see the stages of growth
Bungie went through as they moved from one game to the next. The original game was made by a team of dedicated, talented team of ambitious developers, the second episode was made by a group of people struggling to reclaim the mindset that gave them such organic success, and the final installment was created after a corporate restructure redefined the company's attitude toward their craft.
The point is that the mindset of a developer
Will always have a massive impact on the work they produce. You might notice a similar concept in things you do every day. The first few weeks you spend at a new job are spent making sure you impress the boss and get it all right, and you enjoy yourself because you are experiencing new things. Fast forward to a year later and you are in automated zombie mode. It takes no concious effort to perform what once were intricate tasks and the quality of your work might not have dropped, but has changed.
In games development I think it is important to never lose sight of the fun you have creating. I have had days, weeks and months where I have all but given up on modelling because I open up blender and just stare and the empty workspace in front of me. And I create things in these moments, and they are just... different.