I actually only got into AC a couple of months ago. I picked up the games up to AC3 on PC for 20$ and started playing. Once I got to AC2 I got hooked and played through the Ezio trilogy in like 2 weeks. AC3 was a huge drop off for me however. I was still interested in the Desmond story (Even though I was already spoiled). But I didn't realy like Connor. So I'm still stuck halfway through that game. I will finish it eventually.
As for BF2, I played the first game on several occasions. I played the beta on PC and played it a few times at a friends house on console. However I got bored of it pretty quickly. I don't think I would play that game even 10 hours if I decided to buy it. Part 1 that is. If they do a beta or some free trial through Origin Access I will try it and decide afterwards. If they can pull of the Space battles I might buy it.
This
video does a better job explaining Warframe than I ever could. But to keep it short. It's about grinding for gear to grind for more gear. I know it sounds bad but you should check out that video for a more detailed description