I can say nothing about either FFXIII or DA:A as I've yet to play either but I did, however, plan on writing a review about GoW 3. I suppose this provides me with such an opportunity. I'll will try to keep it spoiler free for those interested in the story but for those of you considering purchasing this game allow me to give you some food for thought.
First, I will say that this game is epic in every way. The boss battles in particular are gorgeous and every bloody second just left me sitting there in awe. The environments are amazingly detailed as well, beautifully rendered. Though often revisited throughout the game, each has its own unique feel and are truly captivating.
The story is fairly well composed and the intro even includes a nice little refresher for anyone not entirely familiar with the series. I think that original fans of the series as well as newcomers both will ultimately, greatly appreciate this as the story unfolds through this final chapter. Though the game does seem to end rather abruptly, I managed to complete it in just under 8.5 hours.
If there were any downsides in my opinion, aside from the length of the overall game, I would have to say it's mostly due to repetition. Many enemies encountered throughout the game have been seen before in previous installments. Not to mention each of the weapons, save one, seem more like spin-offs of the Blades of Athena rather than new material altogether. Again, everything from weapon effects, spells and enemies look gorgeous I found myself a little disappointed that there wasn't any really new, groundbreaking material.
Please don't let this put you off of playing the game however. Overall, it does provide an amazing ending to a story 7 years in the making. Not to mention all of the extra content available upon completion of your first play through. With all of the trophies, challenge modes and collectible items found throughout the game, the game does have a high replay value. Furthermore, I think we'll also see some downloadable content in the near future.
All in all, I would say this game is definitely worth a rental. To the more hardcore fans, if you like testing your mettle and want to really get all those trophies, then playing this game through more than once will be most enjoyable and not feel so much like a chore.