Maybe it isn't fair to compare Samsung's 2015 flagships to LG's big mid-2014 phone. But since some of the G3's specs were ahead of its time last year, let's see how it fares against the Galaxy S6 and Galaxy S6 edge.
Size
The LG G3 is 2-3 percent taller and 6-7 percent wider than the pair of Galaxy S6 flagships. That isn't a huge difference, and you'll want to remember that in a minute, when we get to screen size.
Samsung's phones have a huge thinness advantage, measuring 21-24 percent thinner than the G3.
Weight
Weight is another notch in the Galaxy S6 and GS6 edge's column, as they tip the scales at 8-12 percent lighter.
Build
These are Samsung's first truly premium flagships, with glass (Gorilla Glass 4) backs and aluminum frames.
The G3 doesn't feel overly cheap, but it's clearly trailing here; it's made of a faux metal plastic.
Colors
Your local carrier probably won't offer all of them, but the G3 is available in five different colors.
The blue and green variants of Samsung's phones could end up as the most striking, but US carriers aren't offering those options at launch. They're limiting your choice to black vs. white.
Display (size)
The G3's body isn't bigger by a huge margin, but its screen size has a healthy advantage. It gives you 16 percent more real estate.
Display (resolution)
While HTC (disappointingly) stuck with a 1080p display on its 2015 flagship, LG had already jumped to ultra-sharp Quad HD nearly a year ago. The G3's display was ahead of its time, though the smaller screen sizes on Samsung's phones give them the pixel density advantage.
Display (type)
The Galaxy S6 and GS6 edge mark the first time we've seen an AMOLED display with Quad HD resolution stuffed into such a (relatively) tiny space. Most other Quad HD phones we've seen have been phablets, bigger than the G3.
Curved display
The Galaxy S6 edge has a screen that slopes off on either side. It might sound gimmicky (and perhaps it is, to some degree), but it does add to its aesthetic.
Fingerprint sensor
No more swiping required: Samsung's 2015 flagships have touch-based fingerprint sensors, more in line with Apple's Touch ID sensors (at least on paper … stay tuned for our GS6 review for our full breakdown).
Samsung Pay
We haven't tested it yet, but Samsung's mobile payments service uses a genius technology that tricks swipe-based terminals into thinking it's a credit card. This makes the service nearly universally accepted from Day One.
Processor
This is where the G3 shows its age. Its processor is by no means slow (and its Lollipop upgrade, with ART runtime, should help to smooth out its performance), but the GS6 and GS6 edge should be blazing-fast handsets.
Storage
Samsung's phones have the internal storage advantage, starting on a higher tier and offering three options vs. the G3's two.
MicroSD card
Samsung did, however, drop microSD support from this year's flagships, meaning you can augment the G3's internal storage, but not the GS6es'.
RAM
LG took an unconventional approach to RAM, putting 2 GB in the 16 GB storage model and 3 GB in the 32 GB storage model.
Battery
The G3 had good battery life, though you needed to turn its screen's brightness down a fair bit to get quality uptimes – arguably dampening the effect of its gorgeous Quad HD screen.
Stay tuned for our review, for our impressions of the GS6 and GS6 edge's battery life.
Fast charging
Samsung dropped Qualcomm processors from its big phones this year, but it's still using some form of fast charging – helping you juice up an almost-dead battery faster than you'd expect.
Wireless charging
Samsung also made its 2015 flagships wireless charging enabled, out of the box.
The G3 has that asterisk because its international variant includes wireless charging by default. For its US variant, you need to buy a special battery cover.
Removable battery
You can swap out spare batteries for the G3. This is the first time Samsung has sealed its battery shut (all in the name of achieving those high-end constructions, no doubt).
Camera megapixels (rear)
The Galaxy S6 and edge's rear cameras have higher resolution, but we were very happy with the G3's camera quality. One thing we already know about the GS6's (and edge's) camera is that it fires up lightning-fast.
Camera megapixels (front)
Your selfies will shoot in higher resolution on the Galaxy S6 phones.
Camera aperture
The rear cameras in Samsung's phones have significantly wider aperture.
Laser autofocus
The coolest thing about the G3's camera is that it fires a laser to (almost instantly) measure the distance between phone and subject. Just tap the point on screen that you want in focus, and it takes care of the rest.
Gear VR
The best virtual reality headset you can buy today is the Oculus-powered Samsung Gear VR. There was already a version for the Note 4, but Samsung is also making a new variant that plays nicely with both the Galaxy S6 and GS6 edge.
It isn't likely in the same ballpark of quality, but LG is (in some markets) bundling its own Google Cardboard headset with G3 purchases.
Heart rate sensor
We don't get the impression that this ever became a must-have feature, but Samsung's heart rate sensor returns in the pair of GS6es.
Software
LG was fairly quick in rolling out the Android Lollipop update to the G3, but it still hasn't reached all the major carriers.
The Galaxies launch with Lollipop at their core, and though the familiar Samsung TouchWiz is still sitting on top, it's a thinner layer (with less bloat) this time around.
Release
We wouldn't recommend buying the G3 right now, unless you find a good deal (which you probably can). We'll likely be seeing its successor very soon.
The Galaxy S6 and Galaxy S6 edge officially launch on April 10.
Starting price (full retail)
We put those asterisks in there because full retail prices are varying quite a bit on all three phones. Verizon, for example, has the cheapest pricing on the GS6 and edge – starting at US$600 and $700, respectively. But then T-Mobile has them at $680 and $780, so they're all over the map (but still within that general vicinity).
Starting price (on-contract)
These are more predictable, with $200 and $300 standing as the consistent contract pricing for the Samsung flagships. The G3 does vary here, though, as it's discounted differently by each carrier as it moves towards the end of its initial run.
For more, you can check out Gizmag's reviews of the Galaxy S6, Galaxy S6 edge and LG G3.