Feel Free to Add Comments and Add Any Thing I Missed

SIRI

Siri is an excellent tool that is not matched by the Galaxy S2. Siri acts as your personal assistant and android doesn't have anything nearly as advanced as it. To me this is a major feature and it gives the iPhone an upside. For more info on SIRI you can go to http://www.apple.com/iphone/features/siri.html

Winner: iPhone 4S

Camera & Camcorder

Both phones have 8 mega pixel cameras and front facing cameras. They both have LED flash and can record 1080p video. These are probably some of the best cameras on all smartphones.
If i had to choose witch one or the other i would choose; the iPhone 4S for pictures and the S2 for video recording. Since you will probably be taking pics more often the iPhone is better in this department.

Winner: iPhone

Interface

The iPhone 4S is running iOS 5.0
The Galaxy S2 is running android 2.3
I personally think that the iOS interface is easier to use and can be faster. But that has a downside; there are not nearly as many options as on android. The android market also has apps that apple doesn't allow. The two interfaces are very different and have their own strengths and weaknesses. It is really your choice and what you like better. For more info on the interfaces you can go here,
http://www.pcworld.com/article/219952/google_android_vs_apple_ios_feature_war_heats_up.html

Tie

Screen

Both Screens are bright and crisp. They both have high resolutions and are easy to view.
The Galaxys S2 has samsung top mobile screen; the Super Amoled Plus with a 480x800 resolution.
The iPhone 4S has apple's Retina Display that has a 640x960 resolution.
The main difference in the screens are their size. The iPhones screen is to small for modern day smartphones. 3.5 inches just isn't enough for playing games, watching movies or even everyday use.
The S2 has a 4.3 inch screen and is what i think is perfect.
Even though the iPhone has a higher resolution it is too small to take advantage of and i have to say the Galaxy s2's screen is the winner.

Winner: Samsung Galaxy S2

Hardware

Whats under the hood?
CPU: The iphone 4S has a new dual-core apple A5 clocked at 800 MHz; thats the same as the iPad 2!
The Galaxy S2 has a dual core 1.2 GHz chip.
The S2's processor is faster and can complete tasks faster. Both phones run smoothly and i haven't seen any lag on either phone.
Winner: Galaxy S2

Design

Both the iPhone 4S and Galaxy S2 have beautiful sleek designs. The Galaxy has a slimmer profile at 8.5 mm while iPhone is at 9.3mm. To me this doesn't make that much of a difference; they are both incredibly thin. The Galaxy s2 is also lighter even though its larger profile. Some think too light. The iPhone does look nicer to me and fits better in the hand. Because of its metal casing, it feels solid compared to the S2 witch is made of thin plastic and isn't as durable. Because of the S2's noticeably larger screen, it is a bit larger.

Winner in profile: iPhone 4S