Most video games don't challenge me. It's sad how soft games have become. TBH Skyward Sword, S Mario Galaxy 2 and others were a bit disappointing. Even with new challenge modes and puzzle elements the still felt formulaic and like I was repeating previous challenges. TPrincess was fun but way too easy. Most things have been done in games: you have Myst rip-offs, Zelda/Dungeon busters types, FPS etc, etc. All of them lose their challenge once you're familiar with the formula. Games might be challenging at first but are easy the next play-through.
Here's a list of my favorite challenging games and why they keep my interest where others don't:
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Games started challenging...
Super Mario Bros 1, 3 and World- Okay they're formulaic but SMB1 started it and is challenging even when you know where every cliff and enemy is. SMB3 This was the first and best (imo) expansion of power ups with more control and more onscreen threats like airship cannons etc. The variety and surprises were nice too. Super Mario World- I've 100% cleared this. The secret paths and map really added to the experience. At this point, side scroller Marios still felt fresh and expansions added new things. The gameplay was easier but exploration and the adventure made up for that (flying under the goal to reach a secret goal, etc). After World, side scrolling Marios felt dull and never regained their appeal in a been there, done that way. I don't like the linear level select path system either.
The Zelda series had a similar deal: Zelda 1 was freaking hard, 2 was even harder, you had to be very precise. ALttP and LA got easier with better controls etc but also had a great feel of mystery, quest and exploration.
OoA & OoS were entertaining and had a few annoying puzzles but didn't give the experience that ALttP and LA did.
Several series followed this pattern: Mega Man X 1&2 were very formulaic but hard, although it stayed challenging enough through X5. The 2D Metroid series followed the pattern. Mario Kart. And so on.
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When 3d games came out that made their series fresh again, SMario64, OoT and such brought new life into the series. Even though OoT is super easy now the impact never wore off.
Then games got soft. Difficulty was often from bad camera controls (Sonic games) or misleading platform designs.
The Sonic series was fun, Sonic adventures were worth a few camera kills. Sonic Heroes was when they started to 'fix what wasn't broken' when they should have fixed the camera and AI. Other Sonics repeated this, Black Knight, Unleashed... Unleashed had the best normal sonic gameplay of any Sonic game IMO but they had to add the frustrating night stages. Colors was stupid and easy (puts up flame shield).
Metroid Prime, like OoT captured the metroid spirit in a new 3D form. Prime 2 was challenging but didn't feel right because the dark world and ammo elements. It was still good. 3 had great graphics but that easier, more of the same feel and the story didn't add much.
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So games are hard in good ways because their freshness without fixing what's not broken and challenge where the player has control and must overcome a situation. Not because poor control. Strategy can be included too.
Majora's Mask is arguably the best Zelda, for those who liked it. It was a love it or hate it kind of game. What's important is it had the Zelda spirit and took that to very original, deep new settings with the 3 day time travel twist and Masks. MM didn't fall in OoT's shadow because it had the right stuff mentioned above^. MM had some of the best Zelda dungeons ever: Snowhead, Great Bay Temple, Stone Tower.
The Lost Vikings has to be mentioned. Hard, great puzzles, strategy, good yet simple controls. Tomator might be the hardest final boss ever.
Sonic and the Secret Rings was different enough that once I got used to it the game proved challenging and fun without being a clone or gimmick Sonic.
Metal Arms: Glitch in the System was super hard and super fun. The infinite lives and checkpoint system allowed surprises to kill you without an annoying penalty. You were often seriously out gunned and had to be smart and fast to survive. One of the few American made games that wasn't based off a franchise (Spiderman, Starwars, X-Men, etc) or movie. The voice acting and writing had great American humor.
Metroid Fusion. The new elements and changes worked and kept the challenging old-school feel. What can I say?
MegaMan Zero series brought back the old-school challenge with different enough gameplay than the MMX games. The story was decent for a side scrolling shooter too and wrapped up loose ends from the MMX series. MMZero 1 and 2 were nice and hard, 3 fun but meh and 4 too easy but wrapped up the series.
TP and SS both had great innovative elements and strong points. TP showed that the wii could use motion control in an awesome hard-cord game with beautiful graphics. Buuuuut, when all was said and done they were more of the same and easy :/
Mario Galaxy gave 3D Marios several new dimensions. Even though Galaxy 2 was better in most ways and harder, it was more of the same.
Mario Kart Wii was fun to drive with the steering wheel. Competitively it was more of the same like most Mario Karts after MK64.
I could go on but you get the idea.
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The reason SSBs games have remained popular, including Melee and less-so SSBs 64, (despite the obvious huge imbalance and broken things like certain infinites) is they usually provide a fresh experience, have good controls where the player must be skilled to be good and varying strategy. Playing with people makes this happen. SSBs does provide the necessary tools to make this work. Games like Monster Hunter and some FPSs are fun online experiences but get old eventually. I hope the next SSbs have these winning elements: fresh without fixing what's not broken, challenge where the player has good control and must overcome situations with skill. Not because poor control. And Strategy. While fixing the flaws of Brawl and staying true to the SSBs spirit.