Not a simple Platinum, as it's easy to make a mistake with some trophies. You'll need to play through the game at least six times, to collect all the different endings for each corresponding trophy. The most challenging, however, is the Who Needs A Gun trophy, as it requires a large, specific set of requirements - one of which is saving the game only two times during the entire playthrough. If you make a mistake, you'll need to start over.

This is not a game for anyone searching for a quick Platinum. Expect, minimum, 35 hours of gameplay, if you do some research and planning first. Otherwise, expect far more time required.

A few things to mention before we get started. First, if you pause the game by hitting Select, you will also be pausing the timer. This comes in handy when you want to check any walkthroughs while working on completing the game under the 3 hour limit. Also, after clearing the game the first time, you can hit R1 in the Options menu and add a higher number of bullets under the Bullet Adjustment. Finally, unlike most games which have a master file to track all your progress, Silent Hill 2 HD does not. This means, you'll need to load your results each time you start a new game, otherwise each ending won't be included in your total count.

Now, with that out of the way, we highly recommend simply playing through the first time without worrying about anything. Just enjoy the story and get familiar with the game itself. If you like, you can set the Riddle level on Easy and Action level on Normal. You should unlock a number of story related trophies during this process.

After that, go ahead and do Maria's scenario, which will earn you the Restless Dreams trophy.

Next, set the Action level to Hard and the Riddle to Normal, and begin your second playthrough. Focus on getting the second normal ending.

Then, adjust the Riddle level to Hard, and play for a third time, aiming on getting the third and final normal ending.

Now, you'll need to start working on the special endings. We began with the Rebirth ending, which requires you to find four items: the White Chrism, Book of Lost Memories, Unholy Grail, and the Book of Crimson Ceremony. This will earn you the Say Your Prayers trophy.

For your fifth playthrough, you can aim for the UFO ending, where you'll need to get the Blue Gem and use it in three different locations.

Your sixth and hopefully last playthrough will be for the Dog ending, which requires you to unlock the Observation Room on the third floor of the Alternate Lakeview Hotel using a collected Dog Key. However, you should also check the Who Needs A Gun trophy in the trophy guides in our Links page to see the requirements of acquiring the Green Hyper Spray. During your sixth playthrough, you should be aiming for completing these requirements at the same time. This is not easy, and remember you can only save the game twice, while keeping both the Action and Riddle level on Hard. Completing these requirements will award you with a 10 Big Star result.

Finally, after being awarded the 10 Big Star, load up the game one last time, head to the camper on Saul Street, and inside you'll find the Green Hyper Spray, thereby unlocking the Who Needs A Gun trophy, along with the Platinum.

Good luck!

A great Walkthrough by duck360, which includes videos:
http://www.playstationtrophies.org/forum/silent-hill-2-hd/152152-silent-hill-2-hd-10-star-walkthrough-videos.html

And a Walkthrough on IGN:
http://www.ign.com/wikis/silent-hill-hd-collection/Silent_Hill_2

And a text-based Walkthrough by Alex:
http://www.gamefaqs.com/ps2/437029-silent-hill-2/faqs/34677

Kheapathic has a great Trophy Guide here:
http://www.playstationtrophies.org/game/silent-hill-2-hd/guide/

And a great Trophy Guide here, by trophybot:
http://ps3trophies.com/forums/showwiki.php?title=PS3-Trophy-Guides:Silent-Hill-2-HD-Trophy-Guide

And a Trophy Guide by Platisfaction:
http://psnprofiles.com/guide/3-Silent-Hill-2-HD-Trophy-Guide

Some useful Trophy Guide tips, here:
http://psnprofiles.com/trophies/1380-Silent-Hill-2-HD?guide

Lastly, here's a basic Trophy List:
http://www.playstationtrophies.org/game/silent-hill-2-hd/trophies