This gen for me is largely about the golden age of Bioware. I do need to go back and play many games I missed from this time period, as I didn't have a lot of disposable income during it.
1. Dragon Age : Origins : My second favorite RPG of all time, this game is the closest video games have come to capturing the feeling of Lord of the Rings for me.
2. Mass Effect 1 : A whole new scifi-world to explore, could spend hours just looking at/listening to the codex. Wrex is a GOAT-tier companion.
3. Bioshock : Rapture is an awe-inspiring setting, a place of science turned to glorious madness. One of the greatest plot twists in gaming.
4. Halo Reach : Most of the late 2000s was spent playing Halo games with my friends, either coop or multiplayer. Reach was the pinnacle of this, with Bungie having polished the formula to a tee.
5. Skyrim : As much as it might seem lackluster today playing this vanilla, I was totally engrossed in this game back when it released for hundreds of hours, and thanks to finally having a gaming PC playing this modded helped revitalize my love for it. Mods can only do so much though, the core foundation is still very solid.
6. Dragon's Dogma Dark Arisen : The best combat I've ever experienced in an RPG game, and especially the best magic has ever felt to cast in any game. It's quest structure, characters, main plot, and traversal mechanics leave a lot to be desired or else this would be near or at the top spot. Here's hoping DD2 fixes these issues.
7. Tales of Vesperia : It's rare for RPGs to have a full coop campaign to play through with your friends, so Tales of series has always been a go to for my best friends and I. Vesperia starts off slow, especially in terms of the combat, but once the ball starts rolling it's combat is quite fun, the characters are endearing with Yuri being a great MC, and the worldbuilding unique enough to hold interest through a sometimes meandering main plot.
8. Batman Arkham Asylum : While City's gameplay is overall better, the atmosphere and pacing of Asylum places it at the top of the Arkham games. The Scarecrow sections will be a long lasting memory.
9. Mass Effect 2 : While my opinion of this game has gone down over time for it's failings in progressing RPG mechanics and exploration from the first game, and not properly advancing the plot of the series, it still has one of the best cast of party members in any game(especially Mordin Solus, arguably Bioware's best ever character).
10. Dark Souls : I do think this game takes somewhat of a nose dive in the later parts of it(especially Lost Izalith), but the first half or so of this game is amazing. Top tier level design in particular.