I wouldn't consider a big-ass gunfight to be the "more spectacular" finale. Clearing out an entire tanker (which you started the game on, incidentally) then going to a wedding then hunting down a guy at an abandoned building then clearing out everyone standing in your way then hopping on a bike then JUMPING THE BIKE OFF A RAMP AND CLIMBING INTO A HELICOPTER MID-AIR then following a boat and finally gunning your target down face-to-face on Happiness Island... WOW what an ending! As far as stakes go, GTAV has the bigger stakes... at least as far as the lore is concerned (again, gameplay makes it easy on the player, which makes it seem lower stakes), but going from one gun fight to the next to the next doesn't really wow me next to the series of different stunts you pull off at the end of GTAIV. And in the episodes, you infiltrate a prison for a finale, then you assassinate a target on his private jet and then parachute to safety for another finale. FUCK those are good! Of course, the optional finales for GTAV are pretty incredible, in that they definitely fulfilled that sense of dread that the game was leading up to about losing Trevor or Michael.
However I would firmly disagree that Niko was a much more compelling protagonist than any of the three from GTAV. Even as a fellow Serb, he was just kinda dull. There was ludonarrative dissonance a plenty in how he remorsefully regretted his actions in the Balkan Civil War and wanted to put criminal life behind him, only to mercilessly beat the shit out of everyone he sees and run over pedestrians without a care in the world. Trevor, meanwhile, was consistent in character with his actions. He was introduced as this loose cannon that EVERYONE is either terrified of or detests, but once you "get behind the wheel", you find a real softie at heart, and he has some of the most upstanding morals between the three, considering his value of honesty and loyalty... even if he is a psycho. I would really only say that Johnny is the one character between IV and V that didn't do a whole lot for me. He looks out for his junkie girlfriend/ex no matter how shitty the consequences are, he doesn't really have much solidarity, and by the time of GTAV we find out he has a penchant for hypocrisy now that he's become a junkie, too. Niko and Louis felt a lot alike, and both were likable. More likable than Franklin or Michael or Trevor? Eh... that's up to personal preference.