Fated Summons round 5.
First of all: This is by far the best FS selection we have ever had, of course this should be true every time as we get newer heroes every time. But this time it´s really a big step up from last time.
A little overview over which groups of heroes are currently in the rotation (if you only want hero pick recommendations, feel free to scroll down). And as always, no costumes included.
Hotm: Obviously they will never run out, as they produce 12 per year and only offer 10 in FS, so on average the hotm row grows 1 month older every iteration (in comparison to the current heroes).
CF1 heroes: This is round 3 of 5 in an interesting group. Very old heroes, but some great and timeless functionalities there like still to come are Lady of the Lake and Chameleon in the next 2 rounds, while Black Knight is possible, but not guaranteed.
The seasonal event heroes: Round 2 of 2(?). We will see what new group will be substituted in for them. Maybe CF2? Or they run 1 more round of seasonal heroes including some newer ones.
The end of S1 heroes brings us Season 4: Round 1 of 4. The newest heroes we have ever seen in FS, so as a general rule the heroes in this group will always be among the more interesting ones.
As always
This is a feature mostly designed for people that spend little to no money at all, as all the heroes on this list are badly outdated and will not stand up against a team of current heroes. Still a few heroes can be useful to many players especially some niche heroes.
If you have costumes of of any of the heroes on this list, picking a duplicate may be the best thing to do as you at least get a hero with better stats than what is on offer otherwise.
So lets get to the individual heroes:
Again as always: Damage heroes age faster and these heroes here are among the oldest heroes in the game, so if in doubt skip the damage heroes and go for functionality and healers instead, for a better value hero.
Hotm: A rather bad selection this time, the 2018 family is not nearly as powerful as 2017 compared to last time, but 1 nice hero.
Natalya: A rather bad hero, but not the worst we´ve seen.
Zeline: Attack down and dispel is interesting, but there is no more damage to speak of, so definitely not a top pick. Also this is the first hero that shows up in FS for he second time. SG quality control at it usual top level 
The bloody fools can´t even be bothered to read through 4 old lists to see which ones have been there before.
Alasie: A very outdated damage hero, not interesting.
Delilah: A good class a, a decent heal with bonus minions, makes a rather good package! Definitely the best in the hotm group.
Aeron: A very bad pick.
CF1: Two extra strong choices this time!
Guardian Kong: Since red is a bad color Kong is not the worst choice, cleanse is interesting on a damage hero, but the damage itself is not worth much.
The Hatter: Definitely one of the most interesting heroes this time. Buff stealing is an amazing functionality that is very rare in this game!
Alice: Same as Alasie above, an outdated damage dealer.
Guardian Gazelle: Another absolute top quality choice! A good protection for the team against ailments and damage as well as the gigantic attack boost for both special skills in PvP and tiles against titans!
Boss Wolf: Worst CF1 hero. Very slow speed for nothing interesting.
Seasonal event heroes: A few interesting options and a top pick.
Vanda: Very fast ailment protection is great, plus steals healing. Definitely way better than all the red options in FS4.
Francine: Another hitter with cleanse, but with the same problem as the Gorilla, too low damage.
Krampus: Top class hero! Taunt is an extremely powerful skill!
Roc: Another cleanse on damage hero, but not much there alltogether. And there I was thinking this is rare lol.
Killhare: Used to be a top notch tank a longtime ago 
If someone needs a purple tank, then this one is the best in FS5, if someone needs/wants damage heroes, this one might be the best of the older 3 groups of heroes.
Season 4: Newest group we´ve ever had, so if in doubt, pick one of these heroes. Of course this being in theory the strongest group we´ve ever had in FS, SG tried to pick rather the weakest possible options. So this time we get a lot of heroes with better than usual stats, but not especially exciting abilities (with 1 exception).
Captain Nemo: Not an amazing ability, but see above. A sniper with decent stats and better than usual damage for FS heroes.
Garjammal: See Nemo above, same in green.
Passepartout: Good class and good healer, especially good for defense. Solid choice.
Akkorog: Solid choice for hit-3. Especially good on defense. Probably best damage hero in FS5.
Lepiota: Very surprised to see her on the first round of S4 on the FS. Would have expected Hannah or Moreau, but instead we got an absolute MVP candidate! Amazing and timeless functionality. If there is a real monster on the defense in front of you, well make it go away at fast speed. Yes, thank you very much…
So as a summary:
Top picks:
Lepiota, Krampus, The Hatter and Guardian Gazelle.
All 4 have amazing functionality and depending on each players needs one or another of them will be the top pick. One cannot go wrong with any of them!
For people that really want a red hero: Captain Nemo or Vanda are OK options.
For people that want healers: Passepartout is probably the best healer, but Delilah is also OK.
For people that want damage: Akkorog (hit-3), Killhare (hit-all), Garjammal (sniper), Captain Nemo (sniper).
Have fun with your shiny old toys! May they serve you well!
EDIT: Changed the pic to the actual ingame version and added Vanda as alternative to Nemo (Blame @BobTheSnark for that one!)
But I don´t use him anymore. I never liked him on offense, because he doesn´t synergize well with other hit-3s, but he was on my def team for a very long time, because the raw numbers made him good for that and all the bad things about him don´t matter on defense, some are even a bonus on defense (the shuffle effect).