Now the Halo Reach is going to be released in a few more weeks, I thought about doing a retrospective review of the series. I'll evaluate my views towards each Halo title that were released, I'm not going to dive into the novels or the graphic novel. However, I'll be also be reviewing the beta, as I clearly remember it. My views towards some of the games in the series will be quite controversial amongst fans.  I like to do it as a bit of a tribute to the franchise, as I'm highly anticipating for Reach.
 
Do you think I should do it in blog format or write it in the user review section? 

I would go with the blog unless you plan on doing each game individually. I think it's an awesome idea. 

Yes! I would read it, anyway. 

reviews are less noticeable but that is where it belongs right, since it's a review and if people go looking for a halo review they'll be able to find yours if you make it a review. Hell you could post it twice, that wouldn't be all that bad idk though maybe the mods don't like that.

Yeah. Although by now the older games are so nostalgic I don't know how much of a proper review it would be. MS should just put CE and 2 on the 360 with working online multiplayer over XBL, although LAN parties are still the best part of CE.

I think it depends on how you plan on writing the review.  If it's a monologue not focused on the game(s), then it seems more blog appropriate.  If it would be a review of multiple games, it would certainly make more sense to review them using the "Review" function.