I revisited some data from Codeforces and, after 5 years, decided to calculate again who has participated in the most contests. I took into account all official contest participations, including those where a user participated unofficially. However, I excluded Practice/Virtual contests.

P.S: I think no one will beat ruban ever :)

Rank	Handle	Total	Official	Unofficial
1	ruban	853	829	24
2	kmjp	681	380	301
3	dreamoon_love_AA	637	384	253
4	coderbd	632	610	22
5	PAG	619	609	10
6	natsugiri	614	387	227
7	uwi	602	342	260
8	balakrishnan	590	521	69
9	kzyKT	577	464	113
10	Jimanbanashi	556	389	167
11	_LeMur_	525	402	123
12	Hasan0540	503	347	156
13	KrK	481	299	182
14	Gassa	479	376	103
15	Killever	432	428	4
16	_Dragon_	428	393	35
17	oversolver	424	271	153
18	espr1t	417	379	38
19	xish	416	416	0
20	Um_nik	415	302	113
21	sutekine	411	406	5
22	Golovanov399	410	338	72
23	nuip	407	290	117
24	Farhod	405	275	130
25	leaf1415	395	229	166
26	Zain	394	391	3
27	hank55663	390	262	128
28	eugalt	386	386	0
29	BigBag	379	293	86
30	Egor	374	290	84
31	I_love_Tanya_Romanova	370	260	110
32	flashmt	367	298	69
33	Mukundan314	366	365	1
34	chemthan	364	222	142
35	Azat_Yusupov	357	264	93
36	STommydx	356	286	70
37	ksun48	354	290	64
38	Hyperbolic	354	209	145
39	Egor.Lifar	354	305	49
40	Nero	345	235	110
41	cjoa	341	313	28
42	Tima	341	271	70
43	hogeover30	338	307	31
44	titia	337	216	121
45	Ferume	336	315	21
46	dush1729	335	335	0
47	Kilani	335	237	98
48	MrDindows	333	256	77
49	guille	328	203	125
50	emthrm	328	188	140
51	nhho	327	240	87
52	awoo	327	282	45
53	adamant	326	309	17
54	I_am_Heisenberg	323	323	0
55	codelegend	322	240	82
56	antguz	322	277	45
57	Mujahid	321	321	0
58	zhabo	320	292	28
59	risujiroh	320	210	110
60	Temirulan	318	242	76
61	rsFalse	316	311	5
62	Wandoka	315	302	13
63	abisheka	314	271	43
64	IITianUG	313	312	1
65	rainboy	308	252	56
66	iMurat	308	306	2
67	SlavaSSU	307	247	60
68	torus711	306	272	34
69	maximumSHOT	302	205	97
70	allllekssssa	301	251	50
71	Subhashis_CSE	301	300	1
72	debug	300	299	1
73	bi11a1	300	299	1
74	Ronnie007	300	201	99
75	_Ash__	299	229	70
76	vladmart	298	236	62
77	tourist	298	265	33
78	shahed_ahmed	298	297	1
79	quandum	298	291	7
80	_c_k_r_	298	298	0
81	ScarletS	297	275	22
82	Kawaii	297	297	0
83	TripleM5da	296	209	87
84	Svyat	296	244	52
85	akshay_1	295	295	0
86	shakil_AUST	294	287	7
87	physics0523	294	214	80
88	Ra16bit	294	288	6
89	Lawali	293	225	68
90	ABalobanov	293	210	83
91	P___	292	274	18
92	DatoTS	292	289	3
93	tute7627	291	167	124
94	Taube	291	217	74
95	LayCurse	291	195	96
96	shahidul_brur	290	290	0
97	okuzn	290	284	6
98	Dukkha	290	272	18
99	knightL	289	263	26
100	Xellos	289	263	26