1. Samsung Nexus S
The Nexus One, Google's first foray into the smartphone arena, was an extremely impressive phone; Google continues this tradition, albeit with a different manufacturer, in the Samsung Nexus S. The Nexus S boasts a lightning-fast 1GHz processor which absolutely blows through apps; unless an app is extraordinarily poorly designed, you won't experience anything remotely like lag on this phone. The Super AMOLED display is also beautiful, and one of the nicest available on any Android phone to date.
Another plus for this phone is the OS: It is currently one of the few phones to feature Gingerbread. While other carriers have been pushing Gingerbread out now, the Nexus S was the first with it and it still features prominently as one of the phone's selling points: You get an unadulterated, unmodified, bloatware-free installation of Android as compared to many of the other phones being sold through other providers.
One minor detraction is the lack of an SD card slot: the phone is fixed at 16GB, which will already be too small for many power users.
A final note about the Nexus S is its 4G connectivity; though the first version of the phone shipped without 4G connectivity, Samsung and Google heard the reviews and have since shipped an updated model of the Nexus S complete with 4G connectivity. The 4G is pleasantly quick and, combined with the rest of the features of this phone, ensures that the Nexus S will stay on the top of this list for a long time (at least until Google's next unlocked, carrier-free phone makes its debut!)
2. HTC Thunderbolt / HTC Inspire
(NOTE: The Thunderbolt and Inspire are the same phones, but the Thunderbolt is Verizon-ready and the Inspire is AT&T-ready, thus the reason they are being reviewed as the same phone. I'll refer to it as the Thunderbolt in the review, since that's a cooler name)
HTC has always been one of the top contenders in the smartphone arena; they are well-known for making smartphones that are responsive, fast, and well-made, generally being heavier and more solid than the more plastic-feeling phones some other manufacturers sell. That said, HTC doesn't disappoint with its new phone; the Thunderbolt is built on the next-generation Snapdragon processor, and combined with a new Adreno GPU means the phone really flies.
The major draw here is, of course, the 4G connectivity (on both the Thunderbolt and Inspire). the 4G does make it blazingly fast, but brings with it its own downsides: specifically, the 4G connectivity eats away at battery life at almost that same breakneck velocity. The phone itself also isn't the sleek, smooth beast typical of HTC, like a Nexus One or an Incredible; it is instead a bigger form-factor, more comparable to the Evo. Those of you looking for a smaller phone might be disappointed, but the bigger screen and resolution was certainly welcoming and it didn't feel oversized or fail to fit in my pocket. Overall, a great phone, especially with the 4G connectivity!
3. Motorola Atrix 4G
Motorola gets quite a bit of flak around the Web, mostly in part because of their draconian bootloader policies and other additions that make their Android-based phones just a little less open. That said, however, the Motorola Atrix is an amazing phone. It comes with the new Tegra 2 dual-core processor inside, making it one heck of a fast performer; there's barely any lag when using the phone, even with the heavier load that the custom MOTOBLUR UI seems to sometimes add to Motorola phones.
The phone also comes with 4G connectivity, which of course gives it access to the same blazing speeds as the rest of the phones on this list; combined with the dual-core processor, however, this phone is seriously fast.
The Atrix also comes with a dock that is supposed to turn it into a full-featured laptop; the effect is a bit gimmicky and also very pricey, so we're going to review the phone just as a phone. If this is the sort of thing that appeals to you, however, definitely consider it when you're thinking about the Atrix. It's optional, and as such can only add to the experience if you want it!
4. T-Mobile G2X
The G2X is a fantastic phone: there's no ifs, ands, or buts. Powered by the same CPU as the Atrix 4G, the speeds you get from the T-Mobile are just as blazingly fast. It's got pretty much everything you would want out of a phone: nice IPS display, fast both in terms of phone speed and 4G connectivity, and front and back facing camera. It also has a micro-HDMI slot, as well as expandable memory (up to 32GB).
The only downside to this phone is that it's still running 2.2, though LG has said they will roll out an upgrade very soon. Some people have also incorrectly stated the phone runs a stock version of Android; while the phone does run stock 2.2, it does have some bloat like NFS SHIFT, a custom camera app, custom GPS app, and some other non-stock bloatware that can be annoying. Other than that, however, this phone is amazing and an absolutely great buy for anyone in the market for a super fast phone!
5. Samsung Galaxy S II
Another phone in the line of dual-core, super GPU beasts, the Samsung Galaxy S II is just as fast as the previous two phones on this list, also sporting a dual-core processor along with 4G connectivity. The Super AMOLED screen is beautiful, like the Nexus S, and the phone keeps everything humming along very smoothly.
In fact, the differences between this phone and the G2X are slight; both are amazing phones with great displays and speed. The Galaxy S II does run 2.3, but that probably won't be a problem soon as T-Mobile and LG have said they're going to roll out an update soon. All in all, this one's another great buy (though still pricey!)