I don't believe there is another phone other than a Nexus device that offers a stock experience.
From my observation, it seems that Samsung and Moto usually get updates the fastest and HTC the last. Like I said though, all depends on the make of the phone. And of course nothing comes close to a Nexus in terms of updates.
Ditto on the Nexus. Though an unlocked Nexus is the best bet. The CDMA Nexuses from Verizon and Sprint usually get delayed. The Verizon Galaxy Nexus still hasn't gotten Jelly Bean.
Samsung and Motorola are decent, and HTC is alright. They all suffer from both the OEMs and carriers holding up the update process.
Motorola has gotten a lot better though and has made good on their recent promise to update their RAZR line to Jelly Bean by the end of 2012. Plus they have been pushing to be better at the upgrade process lately. Plus Moto's latest phones now have one of the OEM skins that is closest to stock Android, it's not actually stock, but it's closer than other OEMs skins.
Basically though, if you want a no-compromises device then an unlocked Nexus phone on a GSM network is your best bet. But since that's hard to switch if you've already got service then the best option on the CDMA carriers is the 1+ year old Galaxy Nexus for Sprint or Verizon, though the updates have been upsettingly delayed to put it nicely, while their GSM counterparts have had Jelly Bean for months now. Plus the age is piling on. The Nexus 4 hasn't come to the CDMA networks yet and it's hard to say if it will ever make it.
So in the meantime if you're on Verizon going with a Motorola device introduced last fall then you'll be pretty close to, but not actually running, stock Android. Sprint I'm not quite as aware of their line up but the Optimus G is a really decent handset with a skin that doesn't transgress too far from stock Android, and since it's a cousin to the Nexus 4 (the two share the same motherboard) there's a good chance it'll see upgrades into the near future. There may be a better device for Sprint but that's the best I can think of for your criteria. The Sprint Galaxy Nexus is still aging, but it has at least been getting Jelly Bean updates, or is rumored to get it soon, so at least they're doing a little better than Verizon right now as far as the Galaxy Nexus goes.
So hope this helps! It's long winded but I wanted to go over all the options at your disposal to get the most out of a phone. If you have time then there are, as usual, new handsets around the corner, what with the rumored Motorola X Phone that should be running pure stock and the next version of Android, and is said to be likely to debut at Google's I/O conference in May. But if you're looking for something now then the above options are the best you could do I think.
the original razr and razr maxx don't have jelly bean. Just the HD versions and when I had a nexus before it had jelly bean just signal and battery really stunk. But not getting updates til who knows when stinks. I was hoping there was a phone with good signal and battery than still gets updates FAST like the nexus.