When it comes to collecting or achieving 100%, it depends on whether it's worth it or if it's fun to do so. I mean, if the reward is a fun uber-boss or something that makes the game more fun (like Panzer Dragoon Orta's 'Box Mode' (Level select and pilots/dragons/craft not your own, each with unique playstyles each. Try beating the game with a baby dragon, and someone that doesn't use a fast gun; or with the original Blue Dragon from the original Panzer Dragoon game (Hint: Overpowered. Makes Heavy Wing lvl. 5 look weak))), then it's definitely worth the task.
Other games like Final Fantasy XII had the fun of hunting down or earning more challenging battles to face as you beat the game, some with really rewarding items, or items that lead to rewarding items. The Tournesol was definitely worth my time; also considering I was keeping my levels lower than usual to retain the challenge. Giving myself a fake difficulty setting to keep all hunts entertaining. Heck, I intended to have the uber bosses in that game a dual-match. Challenge the wyrms with lvl. 60-75, and the same battles with lvl. 99. Also a way to see what the time difference and challenge level would be depending on those factors.
As for personal achieving, just recently I was playing through Sonic and Knuckles & Sonic 3, and noticed how fast and high my score was reaching and made it a personal challenge to see if I can break 1 million points. I got close, I was off by 1 perfect special stage (50,000 points maximum). All things considered, I was going no savestates, vanilla (no mods or game genie), and only a mid-game break (Zone 7 (start of Sonic & Knuckles portion) intermission). Regardless of not succeeding, that's still the best score I've collected (ever) with minimal deaths and no continues as well. I only died 31 times the entire run, and beat the game in about 3-4 hours tops (I wasn't timing myself). Not bad considering my score at the end.
I think if I were to re-assess my title, I would be more of a self-imposed challenger achiever. I mean, I tend to do some silly things in games just to see if it's possible and whatnot. Also I find it fun to take down powerful beasts with basic, or joke weaponry. Like taking out a T-Rex with a squad of chickens, to killing off a dragon with a pistol. Yes, I do this kind of stuff more in Garry's Mod, but in other games, if it's possible (or the rules allow it), I will find a way to take something down in the most unusual manner possible. Just watch me play GTA sometime to see some unusual routes I would take to get a job done.