Baldur's Gate II: Best RPG Ever
Would I lie to you? BioWare's 2000 magnum opus is still the best RPG of all time. I'll prove it. With science.
BG2 vs. Oblivion
It says something terrible that no matter how poorly Advanced Dungeons & Dragons was balanced (and the ruleset used in BG2 is hilariously imbalanced, with the inclusion of silly rules like monks and class kits), it pales in comparison to the mess that is Oblivion's system. In BG2 you have the freedom to create massively awesome parties by including whatever mix of the brilliantly written NPCs you wanted. Some combinations are better than others, and certain main character builds are borderline ridiculous (oh hi there, dual-class fighter-mage katana grandmaster!), but it's nigh impossible to gimp your group into unplayability if you pay any attention at all.
Meanwhile, in Oblivion, several advancement paths effectively send you backwards. Not leveling any Endurance-related skills? Have fun with the durability of a newborn kitten wrapped in wet paper towels! Picked Mercantile or Speechcraft as a major? Try not to talk to anyone, because while you get marginally better at a sub-game that nobody cares about, the monsters are out there pumping iron and finding better equipment to eviscerate you with. On the flip side, Oblivion is stupidly easy to break to the point where you're de facto invincible. Try stupid crap like that against a BG2 lich and see how far it gets you.
Furthermore, there are more than five faces on characters in BG2. And the women don't look like ugly men. And the dungeons are actually fun and full of neat side paths and alternate solutions, not filled with boring random monsters. But you get the point.
BG2 vs. Mass Effect
Well, for one thing, BG2 is an RPG with progression and equipment that actually matter and aren't vague nods to those games we used to play in ages past. For another, BG2 has fun, lighthearted bits in it and doesn't rely solely on testosterone-fueled WE HAVE TO SAVE THE GALAXY RIGHT NOW EVERYTHING IS DOOMED BUT SHEPARD IS THE UBERMENSCH HOORAY FASCISM. I dare you to find anything in Mass Effect or the sequel that's as flat-out amusing as Edwin's poorly researched work on the Nether Scroll (spoilers: He turns himself into a girl and is simultaneously upset and intrigued at his new…attributes). And while I lament the fact that you never get a chance to strap Jan and his unbearable turnip blather to a nuclear bomb, you do at least get to rat him out to the cops and go taunt him in his jail cell.
Do I even need to bring up combat? Because there's more to BG2 than "point gun, pull trigger." So that's a plus. You can summon up meat shields to tie up the enemy melee while harassing their spellcasters with ranged attacks. You can stealth up, backstab a dude, and lure his friends into a trap-filled ambush. You can drop entangling webs to block off an enemy group's attack vector while engaging another party. Your creativity is the primary limiting factor in how battles play out.
As for Mass Effect, I'm not saying that there's more tactical thinking in Call of Duty single-player…no wait, that's exactly what I'm saying.
BG2 vs. Final Fantasy X
Let's start with the fact that BG2's ensemble of characters doesn't consist of King *** and the cast of Dawson's Creek. Nobody wants to listen to your problems, Tidus, because they are boring and you are stupid. And we definitely don't want to listen to that godawful fake laugh for fifteen minutes or however long that cutscene goes. Also, Rikku is like sixteen so stop trying to sell her as a sex symbol, ya pervs. BG2 challenges you to help a friend through the emotional fallout of having her husband murdered, explain racism and tolerance to a renegade dark elf, and choose between upholding the duly written law of the land or assisting a good-hearted man caught in the gears of the system. One of these things is obviously better than the other.
But seriously, now. One game has you play the half-divine child of the God of Murder who is trying to prevent a power-hungry mage from ripping the divine essence out of mortals and corrupting it for his own ends. The other dresses up teenage daddy issues in asymmetrical clothing. One doesn't screw around with deadly enemies – powerful mages are quite happy to drop a meteor swarm on your whole group, disintegrate your best friend, and gate in a balor during the time stop they cast on the first round of combat. The other has a final boss that you literally cannot die to.
Any other RPGs you want to front about being better than Baldur's Gate II? Because I'll demolish those weak arguments just as thoroughly.