samsung galaxy s5 vs lg G3 vs oppo find 7a vs lg nexus 5

In gaming:
All devices use the same SoC (CPU & GPU, modem etc) and will play all games without any issue. LG G3 has higher resolution so there may be occasional hiccups but really rarely because mobile games seem not to be able to keep up with new hardware.
UI fluidity etc:
Nexus 5 wins here, no contest. G3 comes second and S5 has some problems with keeping up steady flow of work, because of TouchWiz and such. I haven't used Oppo Find 7a(or 1440p 7 for that matter) yet but I heard some good words about it.
Camera:
LG G3 and S5 are pretty much in the same league, Nexus 5's camera isn't atrocious but it can't compete with Samsung/LG/Apple/Sony's solution. Find 7a has good camera but not as good as G3 or S5. Still better than the Nexus 5.
OS:
They all use Android 4.4(except Find 7a wnich has 4.3 jelly bean and that's pretty much a big no, at least for me). Nexus 5 uses pure Android, no OEM skins so it works super fast, comparably to iPhone, iPad and such iOS devices. G3 isn't that bad, but it's skin is mediocre at best in terms of design and fluidity. S5 and it's TouchWiz... when using this device it's hard to believe that it sports 2.5GHz chip under the hood. Don't know about Oppo again, but given that it's a flagship stuck on old Android is very alarming.
Build quality:
Cheap plastic, all of them. It's not as bad as people make it to be though. I saw many Nexuses(Nexii?) broken and not as many S5s and G3s despite that they are more popular. Find 7a is well made (I used One Plus One wnich is basically Find 7a with better software and it's pretty sturdy, better than the others in my opinion).
Battery life:
S5>G3>Find 7a>Nexus 5. Nexus 5 is pretty awful when it comes to battery life, I wasn't able to get a full day with it but your mileage may vary.
Screen:
Galaxy S5 absolutely dominates here, brightness, color reproduction and it's SAMOLED with its incredible contrast. Nexus 5 and Oppo Find 7a have some pretty good screens comparable to iPhone and the rest, but nothing really outstanding. LG G3, don't get fooled with it. It has super high resolution but it's this phone's greatest fault. The difference between 1080p display is so small it's not worth it. LG G3 1440p screen overheats, and cuts the battery life a lot. The brightness is pretty low, and the color reproduction is mediocre at best.
Conclusion:
If I had to choose from the phones you listed I would take Galaxy S5 or LG G3. In my opinion the best phones right now are: Sony Xperia Z3>Xperia Z2>OnePlus One>Galaxy S5>Moto X 2014>LG G2>LG G3>HTC One M8>Nexus 5. Can't forgive HTC for that 4mpx camera and huge body despite small screen, even though the build quality is superb. LG G3 overheats and battery life is meh thanks to its screen. Nexus 5 has poor camera, battery life and build quality. I would buy Xperia Z3 because it has outstanding battery life and camera, the skin is relatively light(but it's still no pure Android), great build quality, stereo speakers, the screen isn't as good as S5 but's better than LG G3. Here's how battery life compares: http://i.imgur.com/eXpLLzs.png