1. RX-78 Gundam
2. Mazinger Z
3. VF-1S Valkyrie
4. Big O
5. Genesic GaoGaiGar
6. Nu Gundam
7. Escaflowne
8. Gurren Lagann
9. Tetsujin 28
10. Wing Zero
Rationalizations below.
Honorable mention to that Knight of Gold...clearly I need to Netflix Five Star Stories.
RX-78 Gundam: Thanks to this machine, giant robots were never quite the same again after 1979. There are plenty of cooler designs out there, but Gundam will endure for the same reason that Captain Kirk's enterprise does. The Gundam's elegant simplicity has aged quite well and influences future designs to this day. Though the series outfitted it with no shortage of gimmicks, we all really remeraber Gundam for how it struck fear into the hearts of Zeon soldiers with its trademark beam rifle and beam sabers.
Mazinger Z: One of the early, groundbreaking super robots. I'm not the biggest fan of the series it belongs to I don't think, but there's no denying its importance in mecha history. It was also updated effectively in the Shin Mazinger reboot.
VF-1S Valkyrie: I strongly approve of the love this gets. Valkyries deserve respect. All mecha are pretty fantastical as a concept, but transforming fighter plans loaded to the teeth are as close to modern realism as it gets. I respect the pick for the VF-19, but the Valkyries of original Macross are the originals. I can't quite pick the VF-19 for the same reason that I wouldn't pick a Gundam from 0083 over the original. I see the 1S is Roy Focker's model. Good taste guys.
Big O: This machine was excellent. Though clearly inspired by certain predecessors (Giant Robo comes to mind), Big O is very distinct. Gundams tend to be lethal & swift weapons of war, and the more traditional super robots toss out rocket punches and energy attacks and just overpower things with excess. In Big O's case though, it seems to actually work like a giant robot would if one actually worked. It's massive, it packs lots of power, and it has weapons everywhere. But it's also very, VERY slow, making competent piloting essential. It was a titanic clunker. It has all of the awesomeness of a giant robot without any of the crazy excesses that usually go along with the type.
Genesic GaoGaiGar: The spiritual successor to Mazinger Z and the super robots of yore, GaoGaiGar is the defining corabining robot for many people these days. Its diversity of weapons is to be applauded, though when you get down to it its fists are ever its best asset.
Nu Gundam: Somehow it just feels like the most natural successor to the original Gundam; it was the perfect machine for Amuro going into Char's Counterattack. Yeah, it's true, the funnels are neat. Depending on how the OVA goes though, I must say that the Unicorn might give this incarnation a run for its money.
Escaflowne: Awesome for reasons similar to Big O, albeit with a significant fantasy influence. Yeah, I have to agree, the dragon motif & transformation is really something.
Gurren Lagann: Not better than GaoGaiGar, but nonetheless better than any other original super robot from the last 10 years. Not that this is particularly hard to accomplish, but still. There's no realism here whatsoever (even GaoGaiGar originally corabined via vehicles), but its feats were certainly fun to watch.
Tetsujin 28: I was torn between this and Giant Robo; both robots are extremely retro and old school and are even controlled in similar ways. Honestly, I gave it the nod because of Imagawa's 2004 series, where the concept and meaning of its design as a WWII weapon of doom gave the show a serious, dark bent that one definitely wouldn't expect from a show with an opening like this.
Wing Zero: Okay yeah, this is me allowing a special personal favorite in. The concept and colors agree with me, I like the plane form, it basically improves on Wing in every way. So far as "winged" Gundams go, I will say that 00 Raiser has grown on me a lot, and even Freedom has a certain appeal...but there's just something about Zero and the way it's drawn that still appeals to me.