Im In sri lanka, I tried both galaxy s2, and Iphone 4. I really wanted the galaxy s2, because it had a nice and bigger screen, but after using it for only 1 week i got fed up of it. the only nice thing about it is the screen, it has one of the most vibrant screens available. I liked android, But I prefer Ios better, Its only my opinion tho. I think Ios is also capable of installing futuristics tweaks and upgrades... like I have hacked my Iphone 4 to use paid applications for free.. got a customezied wall paper.. remote lock.. etc.. So its similar to Android.. But Still Ios is more simplistic.. Whats missing is the widgets and some other features of android.
To take the full potential of galaxy s2's Dual core processor and Nvidia graphics, a proper game should be delivered and applications which will support dual core activity.. but for now.. gingerbread doesnt support dual core applications...
I would still say Galaxy s2, is good.. dual core processor, RAM 1gb, nvidia graphics, and super amoled screen...
I would give Iphone 4, a 9 and Galaxy s2 a solid 8.. for being one of the best androids available.. it will beat the iphone when android develops applications to take full use of its dual core processor and graphics..