[Multiplatform] Game Series you just stopped playing. Sonic is the correct answer, by the way.

I have to say Pokemon too. I loved it, played through Blue and Yellow, got Stadium 1 and 2. Blue was my first game, Yellow I got because I'm a sucker for Pikachu, and you can get all 3 starters without trading. The adventure itself was alright, but the best part was customizing your team of six pokemon and their moves. A bit unfortunate that I didn't know anyone that played a legit version of the game for me to trade/battle.

The Stadium games were probably my favorite part about the series, regardless of what others may think. These games actually encouraged training your pokemon and using TMs, due to the restrictions placed on each of the competition. I mean, sure you can get into trainer/gym battles in the GBA games, but you can go into most battles with your pokemon at 10+ levels higher than your opponents, and most trainers don't use anything resembling a strategy. In Stadium though, your opponents are varied, and you're pretty much playing on an even playingfield. Also, the opposing pokemon have really unpredictable movelists, or a trainer having pokemon with specific tactics. One that I remember clearly is the Gambler trainers, who outfits all their pokemon with at least one OHKO moves, like Fissure. It's neat that they also put in rental pokemon (and I definately used them for Prime Cup), but they get crappy stats, and the evolved pokemon usually gets really horrible moves. I wouldn't be surprised to see a Squirtle with Hydro Pump while Blastoise gets Bubble.

I got into the card game too, but it got a bit too expensive with the constantly expanding card set. The GBA game was fun for a bit, but it was so sloooooooooow, and not really exciting to play.

Why I stopped playing:
I think it's after I beat Stadium Round 1, and decided to train my Yellow team up to play Prime Cup. The training bit just got really really tedious, going to the Elite 4 billions of times. I maxed out the money counter, bout some stats upgrading stuff, and maxed it again, yet my team still isn't lvl 100 yest. I think, until this day, they're around lvl 94.

I tried to pick up the later games again, but I seem to just stop playing after the first few badges, might be because I play them on emu, or that I stopped following the pokemon list after the first 151. I still understand the appeal, but unless they re-invent the battle mechanics, I don't think it's a series for me anymore (still love the original 151 pkmn though).

A Smash Bros. style game with epic storyline and keeping the stat/move level ups? I'm all for it!


Star Wars Rogue Squadron:
Not sure if it's a series I used to play a lot, but I did recall really liking the original for what little time I spent with it, and loved RS2, even though it was a bit shorter than I would have liked.

Why I stopped playing:
RS3. Sure enough, the two player co-op was pretty awesome, but single player was pretty crappy. On-foot missions were a chore and didn't feel that good. I think what I hated most was the level designs though. I only recall 1 or two that were actually enjoyable, and the rest were annoying as hell when compared to RS2, and also needed a bit more flying missions. Using the ATST and landspeeders were fun for a bit, but honestly not fun enough to take that much time in the canpaign mode.

Jam it back in, in the dark.