Hey,
Games after games, the tech tree remains the same. Sure, depending of your nation, your research strategy will differ, but still... 'same old things' feeling appears rapidly.
A few game have tried to break the mould by proposing slightly changing tech tree, for each game. For example the costs between 2 items differ. Or bonus A is given in tech X in a game, but in tech Y in another. Or bonus A is slightly less interesting in game X than in game Y, but another one is stronger.
There are wider possibilities though. Branching between techs are not always the same, you plug 'intermediary' techs between them, and sometime you have to research tech A to get tech C or tech B to get tech C.
Last possibility, 2 minor bonus are exclusives, sometime one appears in a game, another time it's the other... But the code algorithms knows how to compensate, so that the gameplay is not crippled. If you need a tech that gives +1 prestige, then sometime it can be given from a warfare tech (say for example it is called 'greater glory' and you need to kill 20 units to trigger it), sometime it is a civilization tech.
Oh and by the way, how about having some techs needing more than plain and dumb research points to unlock? Say I have this military tech 'Greater Glory' that needs x research points... but also a total of 20 units killed on map, to unlock itself?
Be imaginative Kael. For now this research tree functions as all research trees I have seen since I play PC games (so some 25 years ago...)