It depends on the pokemon. Some pokemon I prefer the Japanese name (I like Dosaidon to Rhyperior), but then there are others where the English name is more prefered (I like Garbodor more then Datsudosu, and Scyther more then Strike), especially when you consider that Zapdos and Jolteon's Japanese names are Thunder and Thunders respectively.
However, sometimes there are interesting puns found in both languages that can be overlooked. Take Jolteon. Another poster mentioned this about a year ago, but Jolteon's japanese name "Thunders" is actually spelled as "sandasu" (which the kana literally spells out to), which translates to something like "three thousand", as in Jolteon is so fast, you see about three thousand copies. Jolteon is not only the 2nd fastest electric type in the game (only being outsped by Electrode), but also in a 4 way tie for 7th fastest pokemon in the game. This is a cool pun that makes me respect the Japanese name a bit more.
I like Carnivine more then Masukippa due to the fact that Carnivine is just filled with puns about the venus fly trap as opposed to Masukippa which is pretty much just the scientific name for the plant.
Then there are some names that are literally the same name , only translated. Miruhog and Watchog are the exact same, since Miru is japanese for "look" or "to watch".
"Hassamu" and "Hassam" are written the same way in Japanese; consonants other than "n" must be followed by a vowel, which is usually "u". "Hassamu" is the literal kana-by-kana romanization, but the name is officially spelled and pronounced "Hassam". But you're right about the origin; he was confusing it with "hasami" which means scissors.
Whoops, goof on my part. Either way, it's still a pun on sissors in both languages, just spelled slightly different.
As for Douryuuzu, I believe I heard somewhere that a mole is like a underground dragon to the Japanese, which explains the "ryuu"(lit. Dragon) in the name choice and why Iris has one in the anime, but yet the cultural significance is just lost in the US dub.
Currently playing: Animal Crossing DS, Pokemon Platinum/Heartgold(JPN)