Though the Samsung Galaxy S II is the overall superior phone, the Motorola Atrix shouldn't be overlooked. Docking gimmick aside, with its update to 2.3.4 out, the phone is finally what was promised to us.
Dual-Core 1.0GHz (1.2GHz for SGS2)
Gingerbread (2.3.4)
4.0" 960x540 (4.3" 800x480 for SGS2)
1GB RAM (same as SGS2, but Atrix limited by Moto saving 1/3 RAM for laptop dock)
16GB Storage (SGS2 also offers 32GB)
5MP camera (8MP for SGS2)
720p capture (1080p for SGS2, but 1080p planned for Atrix)
1080p playback
Tegra 2 GPU (Mali-400MP for SGS2. SGS2 wins but Atrix still better than most)
1980mAh Battery (1650mAh for SGS2)
USB connection
HDMI output
If you can wait (or willing to import), get the S2, but the Atrix is available in the US now. Either way you can't go wrong.
And regardless of your choice, if you want to make iPhone users jealous, get the spb shell 3D UI. A bit on the expensive side, but will leave others in envy. And runs silky smooth even with live wallpaper.