I am curious as to what your top 2 repeat quests are to date, irrespective of level?
Mine...

1. The Ugly Bug Ball L1
Spot In Other Gardens:Any Fly, Bee, Butterfly or CaterpillarAttract In Your Garden:As above, but 2 of each!Times Completed:108

2. Reach For The Stars L2
Spot In Other Gardens:2 different adult Zodiac WildlifeAttract In Your Garden:As above, but 2 of each!Times Completed:53

My big one is definitely the wriggly quests. I like the ugly bug ball too. So I would have to say those two. :)

I did Winter Wonderland a bunch of times while I was looking for calendar pots. That way, I accomplished several things at the same time, and managed to get some speed-spotting bonuses as well. :-)

I loved all the quests so much.  I repeated the winter one like Trace did and I recall doing the caterpillar one several times too.

Do You Have The Eggs Factor? Level I (Seasonal Quest) - 86 times
Rainforest Run Level III - 60 times
Winter Wonderland Level V (Seasonal Quest) - 60 times

The Ugly Bug Ball
Spot In Other Gardens:Any Fly, Bee, Butterfly or Caterpillar
Attract In Your Garden:As above, but 2 of each!
Times Completed:91

Wrigglies (48 times at level 7, 44 at level 8)
Fairy Nuff (70 times at level 4, 58 times at level 5)

Fairy Nuff  on level 3 - 68 times 
Wrigglies  on level  7 - 30 times
I really  enjoyed the quests  and would be  happy to see more like them in Fairyland 's future

Top 2 repeats:
--Rainforest Run L-3  57 times
--Wriggles L-7 39 times & L-8 also 39 times
MY FAVORITE one of all  L-4 On The Farm (21 times).   I really enjoyed the quests too!   :)

Interesting, let me check :) It seems like I don't have such a high numbers as I see above, my max is 24 and I only have 4 quests total which reached 20 repeats. Must be because I collected as much first time bonuses and speed bonuses as possible, I only ever skipped quests if it took ages to set-up for and it was clear there will be more of the same on higher level (like Space invaders). So I didn't do so many repeats overall...

24x Winter Wonderland Level I
24x Wrigglies Level VIII
23x Fairy Nuff Level V
21x Rainforest Run Level III