I honestly couldn't decide between these two.
On one hand, you have a decent so-bad-it's-hilairious voice synth arcade port,and on the other hand you have what the first Battletoads on NES should have been. (Yes, I know of the original NES version of Battletoads and Double Dragon)
Both are killer fun with two players.
Both have amazing soundtracks.
It's really hard to choose one over the other. And on the other hand, I couldn't slight Brain Lord out of the Honourable Mention spot. (hopefully I avoid this habit in time to come)
Though I enjoy the beat-em-up style of Battletoads and Double Dragon moreso than I do the one-hit-and-you-die-and-everyone-has-guns style of Sunset Riders, there's one thing that Battletoads and Double Dragon just doesn't quite match Sunset Riders on; Boss Battles.
For one, each boss has their own theme music. On the next, they're memorable encounters as well as fun bosses to fight. I specify encounters because Battletoads and Double Dragon just throws one big boss at you; in Sunset Riders, there's always stuff going around to watch out for as well.
For example; the first boss of each game. In Battletoads and Double Dragon (I'm sick of typing that title), Abobo is a huge muscle dude that punches his way through a metal wall. Good intro, but then the fight is just beating him up. In Sunset Riders, you walk up to the house of Simon Greedwell as the boss music rises, just as ol' Simon slowly steps out from a door into the open, taunts you with hilairious early SNES voice synth, then opens fire from behind the cover of two barrels. All the while, minions are popping out of the windows, taking potshots at you alongside what their boss is firing at you. And be careful! When you shoot the barrels Simon is firing from behind of enough, they'll fall onto your head. It's a much more dynamic boss fight than pretty much anything found in Battletoads and Double Dragon.
That said, stage 2 of Sunset Riders can go suck a train. I hate the horse-riding segments of that game. The properly-done hoverbike segment of Battletoads and Double Dragon is much more exciting.
So, I can't choose between the two. They both have their ups and downs, but most importantly, they're great where it counts: Sitting on a couch with a friend as you plow through the baddies, working together right up until it comes to seeing who does better.